Node.js v0.11.14 Manual & Documentation
Table of Contents
- About this Documentation
- Synopsis
- Global Objects
- console
- Timers
- Modules
- Addons
- process
- Exit Codes
- Event: 'exit'
- Event: 'beforeExit'
- Event: 'uncaughtException'
- Signal Events
- process.stdout
- process.stderr
- process.stdin
- process.argv
- process.execPath
- process.execArgv
- process.abort()
- process.chdir(directory)
- process.cwd()
- process.env
- process.exit([code])
- process.exitCode
- process.getgid()
- process.setgid(id)
- process.getuid()
- process.setuid(id)
- process.getgroups()
- process.setgroups(groups)
- process.initgroups(user, extra_group)
- process.version
- process.versions
- process.config
- process.kill(pid, [signal])
- process.pid
- process.title
- process.arch
- process.platform
- process.memoryUsage()
- process.nextTick(callback)
- process.umask([mask])
- process.uptime()
- process.hrtime()
- process.mainModule
- util
- util.debuglog(section)
- util.format(format, [...])
- util.log(string)
- util.inspect(object, [options])
- util.isArray(object)
- util.isRegExp(object)
- util.isDate(object)
- util.isError(object)
- util.inherits(constructor, superConstructor)
- util.deprecate(function, string)
- util.debug(string)
- util.error([...])
- util.puts([...])
- util.print([...])
- util.pump(readableStream, writableStream, [callback])
- Events
- Class: events.EventEmitter
- emitter.addListener(event, listener)
- emitter.on(event, listener)
- emitter.once(event, listener)
- emitter.removeListener(event, listener)
- emitter.removeAllListeners([event])
- emitter.setMaxListeners(n)
- EventEmitter.defaultMaxListeners
- emitter.listeners(event)
- emitter.emit(event, [arg1], [arg2], [...])
- Class Method: EventEmitter.listenerCount(emitter, event)
- Event: 'newListener'
- Event: 'removeListener'
- Class: events.EventEmitter
- Domain
- Buffer
- Class: Buffer
- new Buffer(size)
- new Buffer(array)
- new Buffer(str, [encoding])
- Class Method: Buffer.isEncoding(encoding)
- Class Method: Buffer.isBuffer(obj)
- Class Method: Buffer.byteLength(string, [encoding])
- Class Method: Buffer.concat(list, [totalLength])
- Class Method: Buffer.compare(buf1, buf2)
- buf.length
- buf.write(string, [offset], [length], [encoding])
- buf.toString([encoding], [start], [end])
- buf.toJSON()
- buf[index]
- buf.equals(otherBuffer)
- buf.compare(otherBuffer)
- buf.copy(targetBuffer, [targetStart], [sourceStart], [sourceEnd])
- buf.slice([start], [end])
- buf.readUInt8(offset, [noAssert])
- buf.readUInt16LE(offset, [noAssert])
- buf.readUInt16BE(offset, [noAssert])
- buf.readUInt32LE(offset, [noAssert])
- buf.readUInt32BE(offset, [noAssert])
- buf.readInt8(offset, [noAssert])
- buf.readInt16LE(offset, [noAssert])
- buf.readInt16BE(offset, [noAssert])
- buf.readInt32LE(offset, [noAssert])
- buf.readInt32BE(offset, [noAssert])
- buf.readFloatLE(offset, [noAssert])
- buf.readFloatBE(offset, [noAssert])
- buf.readDoubleLE(offset, [noAssert])
- buf.readDoubleBE(offset, [noAssert])
- buf.writeUInt8(value, offset, [noAssert])
- buf.writeUInt16LE(value, offset, [noAssert])
- buf.writeUInt16BE(value, offset, [noAssert])
- buf.writeUInt32LE(value, offset, [noAssert])
- buf.writeUInt32BE(value, offset, [noAssert])
- buf.writeInt8(value, offset, [noAssert])
- buf.writeInt16LE(value, offset, [noAssert])
- buf.writeInt16BE(value, offset, [noAssert])
- buf.writeInt32LE(value, offset, [noAssert])
- buf.writeInt32BE(value, offset, [noAssert])
- buf.writeFloatLE(value, offset, [noAssert])
- buf.writeFloatBE(value, offset, [noAssert])
- buf.writeDoubleLE(value, offset, [noAssert])
- buf.writeDoubleBE(value, offset, [noAssert])
- buf.fill(value, [offset], [end])
- buffer.INSPECT_MAX_BYTES
- Class: SlowBuffer
- Class: Buffer
- Stream
- API for Stream Consumers
- API for Stream Implementors
- Streams: Under the Hood
- Crypto
- crypto.setEngine(engine, [flags])
- crypto.getCiphers()
- crypto.getHashes()
- crypto.createCredentials(details)
- crypto.createHash(algorithm)
- Class: Hash
- crypto.createHmac(algorithm, key)
- Class: Hmac
- crypto.createCipher(algorithm, password)
- crypto.createCipheriv(algorithm, key, iv)
- Class: Cipher
- crypto.createDecipher(algorithm, password)
- crypto.createDecipheriv(algorithm, key, iv)
- Class: Decipher
- crypto.createSign(algorithm)
- Class: Sign
- crypto.createVerify(algorithm)
- Class: Verify
- crypto.createDiffieHellman(prime_length, [generator])
- crypto.createDiffieHellman(prime, [prime_encoding], [generator], [generator_encoding])
- Class: DiffieHellman
- diffieHellman.verifyError
- diffieHellman.generateKeys([encoding])
- diffieHellman.computeSecret(other_public_key, [input_encoding], [output_encoding])
- diffieHellman.getPrime([encoding])
- diffieHellman.getGenerator([encoding])
- diffieHellman.getPublicKey([encoding])
- diffieHellman.getPrivateKey([encoding])
- diffieHellman.setPublicKey(public_key, [encoding])
- diffieHellman.setPrivateKey(private_key, [encoding])
- crypto.getDiffieHellman(group_name)
- crypto.createECDH(curve_name)
- Class: ECDH
- crypto.pbkdf2(password, salt, iterations, keylen, [digest], callback)
- crypto.pbkdf2Sync(password, salt, iterations, keylen, [digest])
- crypto.randomBytes(size, [callback])
- crypto.pseudoRandomBytes(size, [callback])
- Class: Certificate
- crypto.publicEncrypt(public_key, buffer)
- crypto.privateDecrypt(private_key, buffer)
- crypto.DEFAULT_ENCODING
- Recent API Changes
- TLS (SSL)
- Client-initiated renegotiation attack mitigation
- NPN and SNI
- Perfect Forward Secrecy
- tls.getCiphers()
- tls.createServer(options, [secureConnectionListener])
- tls.connect(options, [callback])
- tls.connect(port, [host], [options], [callback])
- Class: tls.TLSSocket
- new tls.TLSSocket(socket, options)
- tls.createSecureContext(details)
- tls.createSecurePair([context], [isServer], [requestCert], [rejectUnauthorized])
- Class: SecurePair
- Class: tls.Server
- Class: CryptoStream
- Class: tls.TLSSocket
- Event: 'secureConnect'
- Event: 'OCSPResponse'
- tlsSocket.encrypted
- tlsSocket.authorized
- tlsSocket.authorizationError
- tlsSocket.getPeerCertificate([ detailed ])
- tlsSocket.getCipher()
- tlsSocket.renegotiate(options, callback)
- tlsSocket.setMaxSendFragment(size)
- tlsSocket.getSession()
- tlsSocket.getTLSTicket()
- tlsSocket.address()
- tlsSocket.remoteAddress
- tlsSocket.remoteFamily
- tlsSocket.remotePort
- tlsSocket.localAddress
- tlsSocket.localPort
- StringDecoder
- File System
- fs.rename(oldPath, newPath, callback)
- fs.renameSync(oldPath, newPath)
- fs.ftruncate(fd, len, callback)
- fs.ftruncateSync(fd, len)
- fs.truncate(path, len, callback)
- fs.truncateSync(path, len)
- fs.chown(path, uid, gid, callback)
- fs.chownSync(path, uid, gid)
- fs.fchown(fd, uid, gid, callback)
- fs.fchownSync(fd, uid, gid)
- fs.lchown(path, uid, gid, callback)
- fs.lchownSync(path, uid, gid)
- fs.chmod(path, mode, callback)
- fs.chmodSync(path, mode)
- fs.fchmod(fd, mode, callback)
- fs.fchmodSync(fd, mode)
- fs.lchmod(path, mode, callback)
- fs.lchmodSync(path, mode)
- fs.stat(path, callback)
- fs.lstat(path, callback)
- fs.fstat(fd, callback)
- fs.statSync(path)
- fs.lstatSync(path)
- fs.fstatSync(fd)
- fs.link(srcpath, dstpath, callback)
- fs.linkSync(srcpath, dstpath)
- fs.symlink(srcpath, dstpath, [type], callback)
- fs.symlinkSync(srcpath, dstpath, [type])
- fs.readlink(path, callback)
- fs.readlinkSync(path)
- fs.realpath(path, [cache], callback)
- fs.realpathSync(path, [cache])
- fs.unlink(path, callback)
- fs.unlinkSync(path)
- fs.rmdir(path, callback)
- fs.rmdirSync(path)
- fs.mkdir(path, [mode], callback)
- fs.mkdirSync(path, [mode])
- fs.readdir(path, callback)
- fs.readdirSync(path)
- fs.close(fd, callback)
- fs.closeSync(fd)
- fs.open(path, flags, [mode], callback)
- fs.openSync(path, flags, [mode])
- fs.utimes(path, atime, mtime, callback)
- fs.utimesSync(path, atime, mtime)
- fs.futimes(fd, atime, mtime, callback)
- fs.futimesSync(fd, atime, mtime)
- fs.fsync(fd, callback)
- fs.fsyncSync(fd)
- fs.write(fd, buffer, offset, length[, position], callback)
- fs.write(fd, data[, position[, encoding]], callback)
- fs.writeSync(fd, buffer, offset, length[, position])
- fs.writeSync(fd, data[, position[, encoding]])
- fs.read(fd, buffer, offset, length, position, callback)
- fs.readSync(fd, buffer, offset, length, position)
- fs.readFile(filename, [options], callback)
- fs.readFileSync(filename, [options])
- fs.writeFile(filename, data, [options], callback)
- fs.writeFileSync(filename, data, [options])
- fs.appendFile(filename, data, [options], callback)
- fs.appendFileSync(filename, data, [options])
- fs.watchFile(filename, [options], listener)
- fs.unwatchFile(filename, [listener])
- fs.watch(filename, [options], [listener])
- fs.exists(path, callback)
- fs.existsSync(path)
- Class: fs.Stats
- fs.createReadStream(path, [options])
- Class: fs.ReadStream
- fs.createWriteStream(path, [options])
- Class: fs.WriteStream
- Class: fs.FSWatcher
- Path
- net
- net.createServer([options], [connectionListener])
- net.connect(options, [connectionListener])
- net.createConnection(options, [connectionListener])
- net.connect(port, [host], [connectListener])
- net.createConnection(port, [host], [connectListener])
- net.connect(path, [connectListener])
- net.createConnection(path, [connectListener])
- Class: net.Server
- server.listen(port, [host], [backlog], [callback])
- server.listen(path, [callback])
- server.listen(handle, [callback])
- server.listen(options, [callback])
- server.close([callback])
- server.address()
- server.unref()
- server.ref()
- server.maxConnections
- server.connections
- server.getConnections(callback)
- Event: 'listening'
- Event: 'connection'
- Event: 'close'
- Event: 'error'
- Class: net.Socket
- new net.Socket([options])
- socket.connect(port, [host], [connectListener])
- socket.connect(path, [connectListener])
- socket.bufferSize
- socket.setEncoding([encoding])
- socket.write(data, [encoding], [callback])
- socket.end([data], [encoding])
- socket.destroy()
- socket.pause()
- socket.resume()
- socket.setTimeout(timeout, [callback])
- socket.setNoDelay([noDelay])
- socket.setKeepAlive([enable], [initialDelay])
- socket.address()
- socket.unref()
- socket.ref()
- socket.remoteAddress
- socket.remoteFamily
- socket.remotePort
- socket.localAddress
- socket.localPort
- socket.bytesRead
- socket.bytesWritten
- Event: 'lookup'
- Event: 'connect'
- Event: 'data'
- Event: 'end'
- Event: 'timeout'
- Event: 'drain'
- Event: 'error'
- Event: 'close'
- net.isIP(input)
- net.isIPv4(input)
- net.isIPv6(input)
- UDP / Datagram Sockets
- dgram.createSocket(type, [callback])
- dgram.createSocket(options, [callback])
- Class: dgram.Socket
- Event: 'message'
- Event: 'listening'
- Event: 'close'
- Event: 'error'
- socket.send(buf, offset, length, port, address, [callback])
- socket.bind(port, [address], [callback])
- socket.bind(options, [callback])
- socket.close()
- socket.address()
- socket.setBroadcast(flag)
- socket.setTTL(ttl)
- socket.setMulticastTTL(ttl)
- socket.setMulticastLoopback(flag)
- socket.addMembership(multicastAddress, [multicastInterface])
- socket.dropMembership(multicastAddress, [multicastInterface])
- socket.unref()
- socket.ref()
- DNS
- dns.lookupService(address, port, callback)
- dns.resolve(hostname, [rrtype], callback)
- dns.resolve4(hostname, callback)
- dns.resolve6(hostname, callback)
- dns.resolveMx(hostname, callback)
- dns.resolveTxt(hostname, callback)
- dns.resolveSrv(hostname, callback)
- dns.resolveSoa(hostname, callback)
- dns.resolveNs(hostname, callback)
- dns.resolveCname(hostname, callback)
- dns.reverse(ip, callback)
- dns.getServers()
- dns.setServers(servers)
- Error codes
- Supported getaddrinfo flags
- HTTP
- http.METHODS
- http.STATUS_CODES
- http.createServer([requestListener])
- http.createClient([port], [host])
- Class: http.Server
- Event: 'request'
- Event: 'connection'
- Event: 'close'
- Event: 'checkContinue'
- Event: 'connect'
- Event: 'upgrade'
- Event: 'clientError'
- server.listen(port, [hostname], [backlog], [callback])
- server.listen(path, [callback])
- server.listen(handle, [callback])
- server.close([callback])
- server.maxHeadersCount
- server.setTimeout(msecs, callback)
- server.timeout
- Class: http.ServerResponse
- Event: 'close'
- Event: 'finish'
- response.writeContinue()
- response.writeHead(statusCode, [statusMessage], [headers])
- response.setTimeout(msecs, callback)
- response.statusCode
- response.statusMessage
- response.setHeader(name, value)
- response.headersSent
- response.sendDate
- response.getHeader(name)
- response.removeHeader(name)
- response.write(chunk, [encoding])
- response.addTrailers(headers)
- response.end([data], [encoding])
- http.request(options, [callback])
- http.get(options, [callback])
- Class: http.Agent
- http.globalAgent
- Class: http.ClientRequest
- Event: 'response'
- Event: 'socket'
- Event: 'connect'
- Event: 'upgrade'
- Event: 'continue'
- request.flush()
- request.write(chunk, [encoding])
- request.end([data], [encoding])
- request.abort()
- request.setTimeout(timeout, [callback])
- request.setNoDelay([noDelay])
- request.setSocketKeepAlive([enable], [initialDelay])
- http.IncomingMessage
- HTTPS
- URL
- Query String
- punycode
- Readline
- REPL
- Executing JavaScript
- Child Process
- Assert
- assert.fail(actual, expected, message, operator)
- assert(value, message), assert.ok(value, [message])
- assert.equal(actual, expected, [message])
- assert.notEqual(actual, expected, [message])
- assert.deepEqual(actual, expected, [message])
- assert.notDeepEqual(actual, expected, [message])
- assert.strictEqual(actual, expected, [message])
- assert.notStrictEqual(actual, expected, [message])
- assert.throws(block, [error], [message])
- assert.doesNotThrow(block, [message])
- assert.ifError(value)
- TTY
- Zlib
- Examples
- zlib.createGzip([options])
- zlib.createGunzip([options])
- zlib.createDeflate([options])
- zlib.createInflate([options])
- zlib.createDeflateRaw([options])
- zlib.createInflateRaw([options])
- zlib.createUnzip([options])
- Class: zlib.Zlib
- Class: zlib.Gzip
- Class: zlib.Gunzip
- Class: zlib.Deflate
- Class: zlib.Inflate
- Class: zlib.DeflateRaw
- Class: zlib.InflateRaw
- Class: zlib.Unzip
- Convenience Methods
- zlib.deflate(buf, [options], callback)
- zlib.deflateSync(buf, [options])
- zlib.deflateRaw(buf, [options], callback)
- zlib.deflateRawSync(buf, [options])
- zlib.gzip(buf, [options], callback)
- zlib.gzipSync(buf, [options])
- zlib.gunzip(buf, [options], callback)
- zlib.gunzipSync(buf, [options])
- zlib.inflate(buf, [options], callback)
- zlib.inflateSync(buf, [options])
- zlib.inflateRaw(buf, [options], callback)
- zlib.inflateRawSync(buf, [options])
- zlib.unzip(buf, [options], callback)
- zlib.unzipSync(buf, [options])
- Options
- Memory Usage Tuning
- Constants
- os
- Debugger
- Cluster
- How It Works
- cluster.schedulingPolicy
- cluster.settings
- cluster.isMaster
- cluster.isWorker
- Event: 'fork'
- Event: 'online'
- Event: 'listening'
- Event: 'disconnect'
- Event: 'exit'
- Event: 'setup'
- cluster.setupMaster([settings])
- cluster.fork([env])
- cluster.disconnect([callback])
- cluster.worker
- cluster.workers
- Class: Worker
- Smalloc
- Tracing
- Async Listeners
About this Documentation#
The goal of this documentation is to comprehensively explain the Node.js API, both from a reference as well as a conceptual point of view. Each section describes a built-in module or high-level concept.
Where appropriate, property types, method arguments, and the arguments provided to event handlers are detailed in a list underneath the topic heading.
Every .html
document has a corresponding .json
document presenting
the same information in a structured manner. This feature is
experimental, and added for the benefit of IDEs and other utilities that
wish to do programmatic things with the documentation.
Every .html
and .json
file is generated based on the corresponding
.markdown
file in the doc/api/
folder in node's source tree. The
documentation is generated using the tools/doc/generate.js
program.
The HTML template is located at doc/template.html
.
Stability Index#
Throughout the documentation, you will see indications of a section's stability. The Node.js API is still somewhat changing, and as it matures, certain parts are more reliable than others. Some are so proven, and so relied upon, that they are unlikely to ever change at all. Others are brand new and experimental, or known to be hazardous and in the process of being redesigned.
The stability indices are as follows:
Stability: 0 - Deprecated This feature is known to be problematic, and changes are planned. Do not rely on it. Use of the feature may cause warnings. Backwards compatibility should not be expected.
Stability: 1 - Experimental This feature was introduced recently, and may change or be removed in future versions. Please try it out and provide feedback. If it addresses a use-case that is important to you, tell the node core team.
Stability: 2 - Unstable The API is in the process of settling, but has not yet had sufficient real-world testing to be considered stable. Backwards-compatibility will be maintained if reasonable.
Stability: 3 - Stable The API has proven satisfactory, but cleanup in the underlying code may cause minor changes. Backwards-compatibility is guaranteed.
Stability: 4 - API Frozen This API has been tested extensively in production and is unlikely to ever have to change.
Stability: 5 - Locked Unless serious bugs are found, this code will not ever change. Please do not suggest changes in this area; they will be refused.
JSON Output#
Stability: 1 - Experimental
Every HTML file in the markdown has a corresponding JSON file with the same data.
This feature is new as of node v0.6.12. It is experimental.
Synopsis#
An example of a web server written with Node which responds with 'Hello World':
var http = require('http');
http.createServer(function (request, response) {
response.writeHead(200, {'Content-Type': 'text/plain'});
response.end('Hello World\n');
}).listen(8124);
console.log('Server running at http://127.0.0.1:8124/');
To run the server, put the code into a file called example.js
and execute
it with the node program
> node example.js
Server running at http://127.0.0.1:8124/
All of the examples in the documentation can be run similarly.
Global Objects#
These objects are available in all modules. Some of these objects aren't actually in the global scope but in the module scope - this will be noted.
global#
- {Object} The global namespace object.
In browsers, the top-level scope is the global scope. That means that in
browsers if you're in the global scope var something
will define a global
variable. In Node this is different. The top-level scope is not the global
scope; var something
inside a Node module will be local to that module.
process#
- {Object}
The process object. See the process object section.
console#
- {Object}
Used to print to stdout and stderr. See the console section.
Class: Buffer#
- {Function}
Used to handle binary data. See the buffer section
require()#
- {Function}
To require modules. See the Modules section. require
isn't actually a
global but rather local to each module.
require.resolve()#
Use the internal require()
machinery to look up the location of a module,
but rather than loading the module, just return the resolved filename.
require.cache#
- Object
Modules are cached in this object when they are required. By deleting a key
value from this object, the next require
will reload the module.
require.extensions#
Stability: 0 - Deprecated
- Object
Instruct require
on how to handle certain file extensions.
Process files with the extension .sjs
as .js
:
require.extensions['.sjs'] = require.extensions['.js'];
Deprecated In the past, this list has been used to load non-JavaScript modules into Node by compiling them on-demand. However, in practice, there are much better ways to do this, such as loading modules via some other Node program, or compiling them to JavaScript ahead of time.
Since the Module system is locked, this feature will probably never go away. However, it may have subtle bugs and complexities that are best left untouched.
__filename#
- {String}
The filename of the code being executed. This is the resolved absolute path of this code file. For a main program this is not necessarily the same filename used in the command line. The value inside a module is the path to that module file.
Example: running node example.js
from /Users/mjr
console.log(__filename);
// /Users/mjr/example.js
__filename
isn't actually a global but rather local to each module.
__dirname#
- {String}
The name of the directory that the currently executing script resides in.
Example: running node example.js
from /Users/mjr
console.log(__dirname);
// /Users/mjr
__dirname
isn't actually a global but rather local to each module.
module#
- {Object}
A reference to the current module. In particular
module.exports
is used for defining what a module exports and makes
available through require()
.
module
isn't actually a global but rather local to each module.
See the module system documentation for more information.
exports#
A reference to the module.exports
that is shorter to type.
See module system documentation for details on when to use exports
and
when to use module.exports
.
exports
isn't actually a global but rather local to each module.
See the module system documentation for more information.
See the module section for more information.
setTimeout(cb, ms)#
Run callback cb
after at least ms
milliseconds. The actual delay depends
on external factors like OS timer granularity and system load.
The timeout must be in the range of 1-2,147,483,647 inclusive. If the value is outside that range, it's changed to 1 millisecond. Broadly speaking, a timer cannot span more than 24.8 days.
Returns an opaque value that represents the timer.
clearTimeout(t)#
Stop a timer that was previously created with setTimeout()
. The callback will
not execute.
setInterval(cb, ms)#
Run callback cb
repeatedly every ms
milliseconds. Note that the actual
interval may vary, depending on external factors like OS timer granularity and
system load. It's never less than ms
but it may be longer.
The interval must be in the range of 1-2,147,483,647 inclusive. If the value is outside that range, it's changed to 1 millisecond. Broadly speaking, a timer cannot span more than 24.8 days.
Returns an opaque value that represents the timer.
clearInterval(t)#
Stop a timer that was previously created with setInterval()
. The callback
will not execute.
The timer functions are global variables. See the timers section.
console#
Stability: 4 - API Frozen
- Object
For printing to stdout and stderr. Similar to the console object functions provided by most web browsers, here the output is sent to stdout or stderr.
The console functions are synchronous when the destination is a terminal or a file (to avoid lost messages in case of premature exit) and asynchronous when it's a pipe (to avoid blocking for long periods of time).
That is, in the following example, stdout is non-blocking while stderr is blocking:
$ node script.js 2> error.log | tee info.log
In daily use, the blocking/non-blocking dichotomy is not something you should worry about unless you log huge amounts of data.
console.log([data], [...])#
Prints to stdout with newline. This function can take multiple arguments in a
printf()
-like way. Example:
var count = 5;
console.log('count: %d', count);
// prints 'count: 5'
If formatting elements are not found in the first string then util.inspect
is used on each argument. See util.format() for more information.
console.info([data], [...])#
Same as console.log
.
console.error([data], [...])#
Same as console.log
but prints to stderr.
console.warn([data], [...])#
Same as console.error
.
console.dir(obj, [options])#
Uses util.inspect
on obj
and prints resulting string to stdout. This function
bypasses any custom inspect()
function on obj
. An optional options object
may be passed that alters certain aspects of the formatted string:
showHidden
- iftrue
then the object's non-enumerable properties will be shown too. Defaults tofalse
.depth
- tellsinspect
how many times to recurse while formatting the object. This is useful for inspecting large complicated objects. Defaults to2
. To make it recurse indefinitely passnull
.colors
- iftrue
, then the output will be styled with ANSI color codes. Defaults tofalse
. Colors are customizable, see below.
console.time(label)#
Mark a time.
console.timeEnd(label)#
Finish timer, record output. Example:
console.time('100-elements');
for (var i = 0; i < 100; i++) {
;
}
console.timeEnd('100-elements');
// prints 100-elements: 262ms
console.trace(message, [...])#
Print to stderr 'Trace :'
, followed by the formatted message and stack trace
to the current position.
console.assert(value, [message], [...])#
Similar to assert.ok(), but the error message is formatted as
util.format(message...)
.
Timers#
Stability: 5 - Locked
All of the timer functions are globals. You do not need to require()
this module in order to use them.
setTimeout(callback, delay, [arg], [...])#
To schedule execution of a one-time callback
after delay
milliseconds. Returns a
timeoutObject
for possible use with clearTimeout()
. Optionally you can
also pass arguments to the callback.
It is important to note that your callback will probably not be called in exactly
delay
milliseconds - Node.js makes no guarantees about the exact timing of when
the callback will fire, nor of the ordering things will fire in. The callback will
be called as close as possible to the time specified.
clearTimeout(timeoutObject)#
Prevents a timeout from triggering.
setInterval(callback, delay, [arg], [...])#
To schedule the repeated execution of callback
every delay
milliseconds.
Returns a intervalObject
for possible use with clearInterval()
. Optionally
you can also pass arguments to the callback.
clearInterval(intervalObject)#
Stops a interval from triggering.
unref()#
The opaque value returned by setTimeout
and setInterval
also has the method
timer.unref()
which will allow you to create a timer that is active but if
it is the only item left in the event loop won't keep the program running.
If the timer is already unref
d calling unref
again will have no effect.
In the case of setTimeout
when you unref
you create a separate timer that
will wakeup the event loop, creating too many of these may adversely effect
event loop performance -- use wisely.
ref()#
If you had previously unref()
d a timer you can call ref()
to explicitly
request the timer hold the program open. If the timer is already ref
d calling
ref
again will have no effect.
setImmediate(callback, [arg], [...])#
To schedule the "immediate" execution of callback
after I/O events
callbacks and before setTimeout
and setInterval
. Returns an
immediateObject
for possible use with clearImmediate()
. Optionally you
can also pass arguments to the callback.
Callbacks for immediates are queued in the order in which they were created. The entire callback queue is processed every event loop iteration. If you queue an immediate from a inside an executing callback that immediate won't fire until the next event loop iteration.
clearImmediate(immediateObject)#
Stops an immediate from triggering.
Modules#
Stability: 5 - Locked
Node has a simple module loading system. In Node, files and modules are in
one-to-one correspondence. As an example, foo.js
loads the module
circle.js
in the same directory.
The contents of foo.js
:
var circle = require('./circle.js');
console.log( 'The area of a circle of radius 4 is '
+ circle.area(4));
The contents of circle.js
:
var PI = Math.PI;
exports.area = function (r) {
return PI * r * r;
};
exports.circumference = function (r) {
return 2 * PI * r;
};
The module circle.js
has exported the functions area()
and
circumference()
. To add functions and objects to the root of your module,
you can add them to the special exports
object.
Variables local to the module will be private, as though the module was wrapped
in a function. In this example the variable PI
is private to circle.js
.
If you want the root of your module's export to be a function (such as a
constructor) or if you want to export a complete object in one assignment
instead of building it one property at a time, assign it to module.exports
instead of exports
.
Below, bar.js
makes use of the square
module, which exports a constructor:
var square = require('./square.js');
var mySquare = square(2);
console.log('The area of my square is ' + mySquare.area());
The square
module is defined in square.js
:
// assigning to exports will not modify module, must use module.exports
module.exports = function(width) {
return {
area: function() {
return width * width;
}
};
}
The module system is implemented in the require("module")
module.
Cycles#
When there are circular require()
calls, a module might not be
done being executed when it is returned.
Consider this situation:
a.js
:
console.log('a starting');
exports.done = false;
var b = require('./b.js');
console.log('in a, b.done = %j', b.done);
exports.done = true;
console.log('a done');
b.js
:
console.log('b starting');
exports.done = false;
var a = require('./a.js');
console.log('in b, a.done = %j', a.done);
exports.done = true;
console.log('b done');
main.js
:
console.log('main starting');
var a = require('./a.js');
var b = require('./b.js');
console.log('in main, a.done=%j, b.done=%j', a.done, b.done);
When main.js
loads a.js
, then a.js
in turn loads b.js
. At that
point, b.js
tries to load a.js
. In order to prevent an infinite
loop an unfinished copy of the a.js
exports object is returned to the
b.js
module. b.js
then finishes loading, and its exports
object is
provided to the a.js
module.
By the time main.js
has loaded both modules, they're both finished.
The output of this program would thus be:
$ node main.js
main starting
a starting
b starting
in b, a.done = false
b done
in a, b.done = true
a done
in main, a.done=true, b.done=true
If you have cyclic module dependencies in your program, make sure to plan accordingly.
Core Modules#
Node has several modules compiled into the binary. These modules are described in greater detail elsewhere in this documentation.
The core modules are defined in node's source in the lib/
folder.
Core modules are always preferentially loaded if their identifier is
passed to require()
. For instance, require('http')
will always
return the built in HTTP module, even if there is a file by that name.
File Modules#
If the exact filename is not found, then node will attempt to load the
required filename with the added extension of .js
, .json
, and then .node
.
.js
files are interpreted as JavaScript text files, and .json
files are
parsed as JSON text files. .node
files are interpreted as compiled addon
modules loaded with dlopen
.
A module prefixed with '/'
is an absolute path to the file. For
example, require('/home/marco/foo.js')
will load the file at
/home/marco/foo.js
.
A module prefixed with './'
is relative to the file calling require()
.
That is, circle.js
must be in the same directory as foo.js
for
require('./circle')
to find it.
Without a leading '/' or './' to indicate a file, the module is either a
"core module" or is loaded from a node_modules
folder.
If the given path does not exist, require()
will throw an Error with its
code
property set to 'MODULE_NOT_FOUND'
.
Loading from node_modules
Folders#
If the module identifier passed to require()
is not a native module,
and does not begin with '/'
, '../'
, or './'
, then node starts at the
parent directory of the current module, and adds /node_modules
, and
attempts to load the module from that location.
If it is not found there, then it moves to the parent directory, and so on, until the root of the file system is reached.
For example, if the file at '/home/ry/projects/foo.js'
called
require('bar.js')
, then node would look in the following locations, in
this order:
/home/ry/projects/node_modules/bar.js
/home/ry/node_modules/bar.js
/home/node_modules/bar.js
/node_modules/bar.js
This allows programs to localize their dependencies, so that they do not clash.
Folders as Modules#
It is convenient to organize programs and libraries into self-contained
directories, and then provide a single entry point to that library.
There are three ways in which a folder may be passed to require()
as
an argument.
The first is to create a package.json
file in the root of the folder,
which specifies a main
module. An example package.json file might
look like this:
{ "name" : "some-library",
"main" : "./lib/some-library.js" }
If this was in a folder at ./some-library
, then
require('./some-library')
would attempt to load
./some-library/lib/some-library.js
.
This is the extent of Node's awareness of package.json files.
If there is no package.json file present in the directory, then node
will attempt to load an index.js
or index.node
file out of that
directory. For example, if there was no package.json file in the above
example, then require('./some-library')
would attempt to load:
./some-library/index.js
./some-library/index.node
Caching#
Modules are cached after the first time they are loaded. This means
(among other things) that every call to require('foo')
will get
exactly the same object returned, if it would resolve to the same file.
Multiple calls to require('foo')
may not cause the module code to be
executed multiple times. This is an important feature. With it,
"partially done" objects can be returned, thus allowing transitive
dependencies to be loaded even when they would cause cycles.
If you want to have a module execute code multiple times, then export a function, and call that function.
Module Caching Caveats#
Modules are cached based on their resolved filename. Since modules may
resolve to a different filename based on the location of the calling
module (loading from node_modules
folders), it is not a guarantee
that require('foo')
will always return the exact same object, if it
would resolve to different files.
The module
Object#
- {Object}
In each module, the module
free variable is a reference to the object
representing the current module. For convenience, module.exports
is
also accessible via the exports
module-global. module
isn't actually
a global but rather local to each module.
module.exports#
- Object
The module.exports
object is created by the Module system. Sometimes this is not
acceptable; many want their module to be an instance of some class. To do this
assign the desired export object to module.exports
. Note that assigning the
desired object to exports
will simply rebind the local exports
variable,
which is probably not what you want to do.
For example suppose we were making a module called a.js
var EventEmitter = require('events').EventEmitter;
module.exports = new EventEmitter();
// Do some work, and after some time emit
// the 'ready' event from the module itself.
setTimeout(function() {
module.exports.emit('ready');
}, 1000);
Then in another file we could do
var a = require('./a');
a.on('ready', function() {
console.log('module a is ready');
});
Note that assignment to module.exports
must be done immediately. It cannot be
done in any callbacks. This does not work:
x.js:
setTimeout(function() {
module.exports = { a: "hello" };
}, 0);
y.js:
var x = require('./x');
console.log(x.a);
exports alias#
The exports
variable that is available within a module starts as a reference
to module.exports
. As with any variable, if you assign a new value to it, it
is no longer bound to the previous value.
To illustrate the behaviour, imagine this hypothetical implementation of
require()
:
function require(...) {
// ...
function (module, exports) {
// Your module code here
exports = some_func; // re-assigns exports, exports is no longer
// a shortcut, and nothing is exported.
module.exports = some_func; // makes your module export 0
} (module, module.exports);
return module;
}
As a guideline, if the relationship between exports
and module.exports
seems like magic to you, ignore exports
and only use module.exports
.
module.require(id)#
id
String- Return: Object
module.exports
from the resolved module
The module.require
method provides a way to load a module as if
require()
was called from the original module.
Note that in order to do this, you must get a reference to the module
object. Since require()
returns the module.exports
, and the module
is
typically only available within a specific module's code, it must be
explicitly exported in order to be used.
module.id#
- String
The identifier for the module. Typically this is the fully resolved filename.
module.filename#
- String
The fully resolved filename to the module.
module.loaded#
- Boolean
Whether or not the module is done loading, or is in the process of loading.
module.parent#
- Module Object
The module that required this one.
module.children#
- Array
The module objects required by this one.
All Together...#
To get the exact filename that will be loaded when require()
is called, use
the require.resolve()
function.
Putting together all of the above, here is the high-level algorithm in pseudocode of what require.resolve does:
require(X) from module at path Y
1. If X is a core module,
a. return the core module
b. STOP
2. If X begins with './' or '/' or '../'
a. LOAD_AS_FILE(Y + X)
b. LOAD_AS_DIRECTORY(Y + X)
3. LOAD_NODE_MODULES(X, dirname(Y))
4. THROW "not found"
LOAD_AS_FILE(X)
1. If X is a file, load X as JavaScript text. STOP
2. If X.js is a file, load X.js as JavaScript text. STOP
3. If X.json is a file, parse X.json to a JavaScript Object. STOP
4. If X.node is a file, load X.node as binary addon. STOP
LOAD_AS_DIRECTORY(X)
1. If X/package.json is a file,
a. Parse X/package.json, and look for "main" field.
b. let M = X + (json main field)
c. LOAD_AS_FILE(M)
2. If X/index.js is a file, load X/index.js as JavaScript text. STOP
3. If X/index.json is a file, parse X/index.json to a JavaScript object. STOP
4. If X/index.node is a file, load X/index.node as binary addon. STOP
LOAD_NODE_MODULES(X, START)
1. let DIRS=NODE_MODULES_PATHS(START)
2. for each DIR in DIRS:
a. LOAD_AS_FILE(DIR/X)
b. LOAD_AS_DIRECTORY(DIR/X)
NODE_MODULES_PATHS(START)
1. let PARTS = path split(START)
2. let I = count of PARTS - 1
3. let DIRS = []
4. while I >= 0,
a. if PARTS[I] = "node_modules" CONTINUE
c. DIR = path join(PARTS[0 .. I] + "node_modules")
b. DIRS = DIRS + DIR
c. let I = I - 1
5. return DIRS
Loading from the global folders#
If the NODE_PATH
environment variable is set to a colon-delimited list
of absolute paths, then node will search those paths for modules if they
are not found elsewhere. (Note: On Windows, NODE_PATH
is delimited by
semicolons instead of colons.)
Additionally, node will search in the following locations:
- 1:
$HOME/.node_modules
- 2:
$HOME/.node_libraries
- 3:
$PREFIX/lib/node
Where $HOME
is the user's home directory, and $PREFIX
is node's
configured node_prefix
.
These are mostly for historic reasons. You are highly encouraged to
place your dependencies locally in node_modules
folders. They will be
loaded faster, and more reliably.
Accessing the main module#
When a file is run directly from Node, require.main
is set to its
module
. That means that you can determine whether a file has been run
directly by testing
require.main === module
For a file foo.js
, this will be true
if run via node foo.js
, but
false
if run by require('./foo')
.
Because module
provides a filename
property (normally equivalent to
__filename
), the entry point of the current application can be obtained
by checking require.main.filename
.
Addenda: Package Manager Tips#
The semantics of Node's require()
function were designed to be general
enough to support a number of sane directory structures. Package manager
programs such as dpkg
, rpm
, and npm
will hopefully find it possible to
build native packages from Node modules without modification.
Below we give a suggested directory structure that could work:
Let's say that we wanted to have the folder at
/usr/lib/node/<some-package>/<some-version>
hold the contents of a
specific version of a package.
Packages can depend on one another. In order to install package foo
, you
may have to install a specific version of package bar
. The bar
package
may itself have dependencies, and in some cases, these dependencies may even
collide or form cycles.
Since Node looks up the realpath
of any modules it loads (that is,
resolves symlinks), and then looks for their dependencies in the
node_modules
folders as described above, this situation is very simple to
resolve with the following architecture:
/usr/lib/node/foo/1.2.3/
- Contents of thefoo
package, version 1.2.3./usr/lib/node/bar/4.3.2/
- Contents of thebar
package thatfoo
depends on./usr/lib/node/foo/1.2.3/node_modules/bar
- Symbolic link to/usr/lib/node/bar/4.3.2/
./usr/lib/node/bar/4.3.2/node_modules/*
- Symbolic links to the packages thatbar
depends on.
Thus, even if a cycle is encountered, or if there are dependency conflicts, every module will be able to get a version of its dependency that it can use.
When the code in the foo
package does require('bar')
, it will get the
version that is symlinked into /usr/lib/node/foo/1.2.3/node_modules/bar
.
Then, when the code in the bar
package calls require('quux')
, it'll get
the version that is symlinked into
/usr/lib/node/bar/4.3.2/node_modules/quux
.
Furthermore, to make the module lookup process even more optimal, rather
than putting packages directly in /usr/lib/node
, we could put them in
/usr/lib/node_modules/<name>/<version>
. Then node will not bother
looking for missing dependencies in /usr/node_modules
or /node_modules
.
In order to make modules available to the node REPL, it might be useful to
also add the /usr/lib/node_modules
folder to the $NODE_PATH
environment
variable. Since the module lookups using node_modules
folders are all
relative, and based on the real path of the files making the calls to
require()
, the packages themselves can be anywhere.
Addons#
Addons are dynamically linked shared objects. They can provide glue to C and C++ libraries. The API (at the moment) is rather complex, involving knowledge of several libraries:
V8 JavaScript, a C++ library. Used for interfacing with JavaScript: creating objects, calling functions, etc. Documented mostly in the
v8.h
header file (deps/v8/include/v8.h
in the Node source tree), which is also available online.libuv, C event loop library. Anytime one needs to wait for a file descriptor to become readable, wait for a timer, or wait for a signal to be received one will need to interface with libuv. That is, if you perform any I/O, libuv will need to be used.
Internal Node libraries. Most importantly is the
node::ObjectWrap
class which you will likely want to derive from.Others. Look in
deps/
for what else is available.
Node statically compiles all its dependencies into the executable. When compiling your module, you don't need to worry about linking to any of these libraries.
All of the following examples are available for download and may be used as a starting-point for your own Addon.
Hello world#
To get started let's make a small Addon which is the C++ equivalent of the following JavaScript code:
module.exports.hello = function() { return 'world'; };
First we create a file hello.cc
:
// hello.cc
#include <node.h>
using namespace v8;
void Method(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
args.GetReturnValue().Set(String::NewFromUtf8(isolate, "world"));
}
void init(Handle<Object> exports) {
NODE_SET_METHOD(exports, "hello", Method);
}
NODE_MODULE(addon, init)
Note that all Node addons must export an initialization function:
void Initialize (Handle<Object> exports);
NODE_MODULE(module_name, Initialize)
There is no semi-colon after NODE_MODULE
as it's not a function (see
node.h
).
The module_name
needs to match the filename of the final binary (minus the
.node suffix).
The source code needs to be built into addon.node
, the binary Addon. To
do this we create a file called binding.gyp
which describes the configuration
to build your module in a JSON-like format. This file gets compiled by
node-gyp.
{
"targets": [
{
"target_name": "addon",
"sources": [ "hello.cc" ]
}
]
}
The next step is to generate the appropriate project build files for the
current platform. Use node-gyp configure
for that.
Now you will have either a Makefile
(on Unix platforms) or a vcxproj
file
(on Windows) in the build/
directory. Next invoke the node-gyp build
command.
Now you have your compiled .node
bindings file! The compiled bindings end up
in build/Release/
.
You can now use the binary addon in a Node project hello.js
by pointing
require
to the recently built hello.node
module:
// hello.js
var addon = require('./build/Release/addon');
console.log(addon.hello()); // 'world'
Please see patterns below for further information or
https://github.com/arturadib/node-qt for an example in production.
Addon patterns#
Below are some addon patterns to help you get started. Consult the online v8 reference for help with the various v8 calls, and v8's Embedder's Guide for an explanation of several concepts used such as handles, scopes, function templates, etc.
In order to use these examples you need to compile them using node-gyp
.
Create the following binding.gyp
file:
{
"targets": [
{
"target_name": "addon",
"sources": [ "addon.cc" ]
}
]
}
In cases where there is more than one .cc
file, simply add the file name to
the sources
array, e.g.:
"sources": ["addon.cc", "myexample.cc"]
Now that you have your binding.gyp
ready, you can configure and build the
addon:
$ node-gyp configure build
Function arguments#
The following pattern illustrates how to read arguments from JavaScript
function calls and return a result. This is the main and only needed source
addon.cc
:
// addon.cc
#include <node.h>
using namespace v8;
void Add(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
if (args.Length() < 2) {
isolate->ThrowException(Exception::TypeError(
String::NewFromUtf8(isolate, "Wrong number of arguments")));
return;
}
if (!args[0]->IsNumber() || !args[1]->IsNumber()) {
isolate->ThrowException(Exception::TypeError(
String::NewFromUtf8(isolate, "Wrong arguments")));
return;
}
double value = args[0]->NumberValue() + args[1]->NumberValue();
Local<Number> num = Number::New(isolate, value);
args.GetReturnValue().Set(num);
}
void Init(Handle<Object> exports) {
NODE_SET_METHOD(exports, "add", Add);
}
NODE_MODULE(addon, Init)
You can test it with the following JavaScript snippet:
// test.js
var addon = require('./build/Release/addon');
console.log( 'This should be eight:', addon.add(3,5) );
Callbacks#
You can pass JavaScript functions to a C++ function and execute them from
there. Here's addon.cc
:
// addon.cc
#include <node.h>
using namespace v8;
void RunCallback(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
Local<Function> cb = Local<Function>::Cast(args[0]);
const unsigned argc = 1;
Local<Value> argv[argc] = { String::NewFromUtf8(isolate, "hello world") };
cb->Call(isolate->GetCurrentContext()->Global(), argc, argv);
}
void Init(Handle<Object> exports, Handle<Object> module) {
NODE_SET_METHOD(module, "exports", RunCallback);
}
NODE_MODULE(addon, Init)
Note that this example uses a two-argument form of Init()
that receives
the full module
object as the second argument. This allows the addon
to completely overwrite exports
with a single function instead of
adding the function as a property of exports
.
To test it run the following JavaScript snippet:
// test.js
var addon = require('./build/Release/addon');
addon(function(msg){
console.log(msg); // 'hello world'
});
Object factory#
You can create and return new objects from within a C++ function with this
addon.cc
pattern, which returns an object with property msg
that echoes
the string passed to createObject()
:
// addon.cc
#include <node.h>
using namespace v8;
void CreateObject(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
Local<Object> obj = Object::New(isolate);
obj->Set(String::NewFromUtf8(isolate, "msg"), args[0]->ToString());
args.GetReturnValue().Set(obj);
}
void Init(Handle<Object> exports, Handle<Object> module) {
NODE_SET_METHOD(module, "exports", CreateObject);
}
NODE_MODULE(addon, Init)
To test it in JavaScript:
// test.js
var addon = require('./build/Release/addon');
var obj1 = addon('hello');
var obj2 = addon('world');
console.log(obj1.msg+' '+obj2.msg); // 'hello world'
Function factory#
This pattern illustrates how to create and return a JavaScript function that wraps a C++ function:
// addon.cc
#include <node.h>
using namespace v8;
void MyFunction(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
args.GetReturnValue().Set(String::NewFromUtf8(isolate, "hello world"));
}
void CreateFunction(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, MyFunction);
Local<Function> fn = tpl->GetFunction();
// omit this to make it anonymous
fn->SetName(String::NewFromUtf8(isolate, "theFunction"));
args.GetReturnValue().Set(fn);
}
void Init(Handle<Object> exports, Handle<Object> module) {
NODE_SET_METHOD(module, "exports", CreateFunction);
}
NODE_MODULE(addon, Init)
To test:
// test.js
var addon = require('./build/Release/addon');
var fn = addon();
console.log(fn()); // 'hello world'
Wrapping C++ objects#
Here we will create a wrapper for a C++ object/class MyObject
that can be
instantiated in JavaScript through the new
operator. First prepare the main
module addon.cc
:
// addon.cc
#include <node.h>
#include "myobject.h"
using namespace v8;
void InitAll(Handle<Object> exports) {
MyObject::Init(exports);
}
NODE_MODULE(addon, InitAll)
Then in myobject.h
make your wrapper inherit from node::ObjectWrap
:
// myobject.h
#ifndef MYOBJECT_H
#define MYOBJECT_H
#include <node.h>
#include <node_object_wrap.h>
class MyObject : public node::ObjectWrap {
public:
static void Init(v8::Handle<v8::Object> exports);
private:
explicit MyObject(double value = 0);
~MyObject();
static void New(const v8::FunctionCallbackInfo<v8::Value>& args);
static void PlusOne(const v8::FunctionCallbackInfo<v8::Value>& args);
static v8::Persistent<v8::Function> constructor;
double value_;
};
#endif
And in myobject.cc
implement the various methods that you want to expose.
Here we expose the method plusOne
by adding it to the constructor's
prototype:
// myobject.cc
#include "myobject.h"
using namespace v8;
Persistent<Function> MyObject::constructor;
MyObject::MyObject(double value) : value_(value) {
}
MyObject::~MyObject() {
}
void MyObject::Init(Handle<Object> exports) {
Isolate* isolate = Isolate::GetCurrent();
// Prepare constructor template
Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);
tpl->SetClassName(String::NewFromUtf8(isolate, "MyObject"));
tpl->InstanceTemplate()->SetInternalFieldCount(1);
// Prototype
NODE_SET_PROTOTYPE_METHOD(tpl, "plusOne", PlusOne);
constructor.Reset(isolate, tpl->GetFunction());
exports->Set(String::NewFromUtf8(isolate, "MyObject"),
tpl->GetFunction());
}
void MyObject::New(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
if (args.IsConstructCall()) {
// Invoked as constructor: `new MyObject(...)`
double value = args[0]->IsUndefined() ? 0 : args[0]->NumberValue();
MyObject* obj = new MyObject(value);
obj->Wrap(args.This());
args.GetReturnValue().Set(args.This());
} else {
// Invoked as plain function `MyObject(...)`, turn into construct call.
const int argc = 1;
Local<Value> argv[argc] = { args[0] };
Local<Function> cons = Local<Function>::New(isolate, constructor);
args.GetReturnValue().Set(cons->NewInstance(argc, argv));
}
}
void MyObject::PlusOne(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
MyObject* obj = ObjectWrap::Unwrap<MyObject>(args.Holder());
obj->value_ += 1;
args.GetReturnValue().Set(Number::New(isolate, obj->value_));
}
Test it with:
// test.js
var addon = require('./build/Release/addon');
var obj = new addon.MyObject(10);
console.log( obj.plusOne() ); // 11
console.log( obj.plusOne() ); // 12
console.log( obj.plusOne() ); // 13
Factory of wrapped objects#
This is useful when you want to be able to create native objects without
explicitly instantiating them with the new
operator in JavaScript, e.g.
var obj = addon.createObject();
// instead of:
// var obj = new addon.Object();
Let's register our createObject
method in addon.cc
:
// addon.cc
#include <node.h>
#include "myobject.h"
using namespace v8;
void CreateObject(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
MyObject::NewInstance(args);
}
void InitAll(Handle<Object> exports, Handle<Object> module) {
MyObject::Init();
NODE_SET_METHOD(module, "exports", CreateObject);
}
NODE_MODULE(addon, InitAll)
In myobject.h
we now introduce the static method NewInstance
that takes
care of instantiating the object (i.e. it does the job of new
in JavaScript):
// myobject.h
#ifndef MYOBJECT_H
#define MYOBJECT_H
#include <node.h>
#include <node_object_wrap.h>
class MyObject : public node::ObjectWrap {
public:
static void Init();
static void NewInstance(const v8::FunctionCallbackInfo<v8::Value>& args);
private:
explicit MyObject(double value = 0);
~MyObject();
static void New(const v8::FunctionCallbackInfo<v8::Value>& args);
static void PlusOne(const v8::FunctionCallbackInfo<v8::Value>& args);
static v8::Persistent<v8::Function> constructor;
double value_;
};
#endif
The implementation is similar to the above in myobject.cc
:
// myobject.cc
#include <node.h>
#include "myobject.h"
using namespace v8;
Persistent<Function> MyObject::constructor;
MyObject::MyObject(double value) : value_(value) {
}
MyObject::~MyObject() {
}
void MyObject::Init() {
Isolate* isolate = Isolate::GetCurrent();
// Prepare constructor template
Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);
tpl->SetClassName(String::NewFromUtf8(isolate, "MyObject"));
tpl->InstanceTemplate()->SetInternalFieldCount(1);
// Prototype
NODE_SET_PROTOTYPE_METHOD(tpl, "plusOne", PlusOne);
constructor.Reset(isolate, tpl->GetFunction());
}
void MyObject::New(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
if (args.IsConstructCall()) {
// Invoked as constructor: `new MyObject(...)`
double value = args[0]->IsUndefined() ? 0 : args[0]->NumberValue();
MyObject* obj = new MyObject(value);
obj->Wrap(args.This());
args.GetReturnValue().Set(args.This());
} else {
// Invoked as plain function `MyObject(...)`, turn into construct call.
const int argc = 1;
Local<Value> argv[argc] = { args[0] };
Local<Function> cons = Local<Function>::New(isolate, constructor);
args.GetReturnValue().Set(cons->NewInstance(argc, argv));
}
}
void MyObject::NewInstance(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
const unsigned argc = 1;
Handle<Value> argv[argc] = { args[0] };
Local<Function> cons = Local<Function>::New(isolate, constructor);
Local<Object> instance = cons->NewInstance(argc, argv);
args.GetReturnValue().Set(instance);
}
void MyObject::PlusOne(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
MyObject* obj = ObjectWrap::Unwrap<MyObject>(args.Holder());
obj->value_ += 1;
args.GetReturnValue().Set(Number::New(isolate, obj->value_));
}
Test it with:
// test.js
var createObject = require('./build/Release/addon');
var obj = createObject(10);
console.log( obj.plusOne() ); // 11
console.log( obj.plusOne() ); // 12
console.log( obj.plusOne() ); // 13
var obj2 = createObject(20);
console.log( obj2.plusOne() ); // 21
console.log( obj2.plusOne() ); // 22
console.log( obj2.plusOne() ); // 23
Passing wrapped objects around#
In addition to wrapping and returning C++ objects, you can pass them around
by unwrapping them with Node's node::ObjectWrap::Unwrap
helper function.
In the following addon.cc
we introduce a function add()
that can take on two
MyObject
objects:
// addon.cc
#include <node.h>
#include <node_object_wrap.h>
#include "myobject.h"
using namespace v8;
void CreateObject(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
MyObject::NewInstance(args);
}
void Add(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
MyObject* obj1 = node::ObjectWrap::Unwrap<MyObject>(
args[0]->ToObject());
MyObject* obj2 = node::ObjectWrap::Unwrap<MyObject>(
args[1]->ToObject());
double sum = obj1->value() + obj2->value();
args.GetReturnValue().Set(Number::New(isolate, sum));
}
void InitAll(Handle<Object> exports) {
MyObject::Init();
NODE_SET_METHOD(exports, "createObject", CreateObject);
NODE_SET_METHOD(exports, "add", Add);
}
NODE_MODULE(addon, InitAll)
To make things interesting we introduce a public method in myobject.h
so we
can probe private values after unwrapping the object:
// myobject.h
#ifndef MYOBJECT_H
#define MYOBJECT_H
#include <node.h>
#include <node_object_wrap.h>
class MyObject : public node::ObjectWrap {
public:
static void Init();
static void NewInstance(const v8::FunctionCallbackInfo<v8::Value>& args);
inline double value() const { return value_; }
private:
explicit MyObject(double value = 0);
~MyObject();
static void New(const v8::FunctionCallbackInfo<v8::Value>& args);
static v8::Persistent<v8::Function> constructor;
double value_;
};
#endif
The implementation of myobject.cc
is similar as before:
// myobject.cc
#include <node.h>
#include "myobject.h"
using namespace v8;
Persistent<Function> MyObject::constructor;
MyObject::MyObject(double value) : value_(value) {
}
MyObject::~MyObject() {
}
void MyObject::Init() {
Isolate* isolate = Isolate::GetCurrent();
// Prepare constructor template
Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);
tpl->SetClassName(String::NewFromUtf8(isolate, "MyObject"));
tpl->InstanceTemplate()->SetInternalFieldCount(1);
constructor.Reset(isolate, tpl->GetFunction());
}
void MyObject::New(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
if (args.IsConstructCall()) {
// Invoked as constructor: `new MyObject(...)`
double value = args[0]->IsUndefined() ? 0 : args[0]->NumberValue();
MyObject* obj = new MyObject(value);
obj->Wrap(args.This());
args.GetReturnValue().Set(args.This());
} else {
// Invoked as plain function `MyObject(...)`, turn into construct call.
const int argc = 1;
Local<Value> argv[argc] = { args[0] };
Local<Function> cons = Local<Function>::New(isolate, constructor);
args.GetReturnValue().Set(cons->NewInstance(argc, argv));
}
}
void MyObject::NewInstance(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = Isolate::GetCurrent();
HandleScope scope(isolate);
const unsigned argc = 1;
Handle<Value> argv[argc] = { args[0] };
Local<Function> cons = Local<Function>::New(isolate, constructor);
Local<Object> instance = cons->NewInstance(argc, argv);
args.GetReturnValue().Set(instance);
}
Test it with:
// test.js
var addon = require('./build/Release/addon');
var obj1 = addon.createObject(10);
var obj2 = addon.createObject(20);
var result = addon.add(obj1, obj2);
console.log(result); // 30
process#
The process
object is a global object and can be accessed from anywhere.
It is an instance of EventEmitter.
Exit Codes#
Node will normally exit with a 0
status code when no more async
operations are pending. The following status codes are used in other
cases:
1
Uncaught Fatal Exception - There was an uncaught exception, and it was not handled by a domain or anuncaughtException
event handler.2
- Unused (reserved by Bash for builtin misuse)3
Internal JavaScript Parse Error - The JavaScript source code internal in Node's bootstrapping process caused a parse error. This is extremely rare, and generally can only happen during development of Node itself.4
Internal JavaScript Evaluation Failure - The JavaScript source code internal in Node's bootstrapping process failed to return a function value when evaluated. This is extremely rare, and generally can only happen during development of Node itself.5
Fatal Error - There was a fatal unrecoverable error in V8. Typically a message will be printed to stderr with the prefixFATAL ERROR
.6
Non-function Internal Exception Handler - There was an uncaught exception, but the internal fatal exception handler function was somehow set to a non-function, and could not be called.7
Internal Exception Handler Run-Time Failure - There was an uncaught exception, and the internal fatal exception handler function itself threw an error while attempting to handle it. This can happen, for example, if aprocess.on('uncaughtException')
ordomain.on('error')
handler throws an error.8
- Unused. In previous versions of Node, exit code 8 sometimes indicated an uncaught exception.9
- Invalid Argument - Either an unknown option was specified, or an option requiring a value was provided without a value.10
Internal JavaScript Run-Time Failure - The JavaScript source code internal in Node's bootstrapping process threw an error when the bootstrapping function was called. This is extremely rare, and generally can only happen during development of Node itself.12
Invalid Debug Argument - The--debug
and/or--debug-brk
options were set, but an invalid port number was chosen.>128
Signal Exits - If Node receives a fatal signal such asSIGKILL
orSIGHUP
, then its exit code will be128
plus the value of the signal code. This is a standard Unix practice, since exit codes are defined to be 7-bit integers, and signal exits set the high-order bit, and then contain the value of the signal code.
Event: 'exit'#
Emitted when the process is about to exit. There is no way to prevent the
exiting of the event loop at this point, and once all exit
listeners have
finished running the process will exit. Therefore you must only perform
synchronous operations in this handler. This is a good hook to perform
checks on the module's state (like for unit tests). The callback takes one
argument, the code the process is exiting with.
Example of listening for exit
:
process.on('exit', function(code) {
// do *NOT* do this
setTimeout(function() {
console.log('This will not run');
}, 0);
console.log('About to exit with code:', code);
});
Event: 'beforeExit'#
This event is emitted when node empties it's event loop and has nothing else to schedule. Normally, node exits when there is no work scheduled, but a listener for 'beforeExit' can make asynchronous calls, and cause node to continue.
'beforeExit' is not emitted for conditions causing explicit termination, such as
process.exit()
or uncaught exceptions, and should not be used as an
alternative to the 'exit' event unless the intention is to schedule more work.
Event: 'uncaughtException'#
Emitted when an exception bubbles all the way back to the event loop. If a listener is added for this exception, the default action (which is to print a stack trace and exit) will not occur.
Example of listening for uncaughtException
:
process.on('uncaughtException', function(err) {
console.log('Caught exception: ' + err);
});
setTimeout(function() {
console.log('This will still run.');
}, 500);
// Intentionally cause an exception, but don't catch it.
nonexistentFunc();
console.log('This will not run.');
Note that uncaughtException
is a very crude mechanism for exception
handling.
Don't use it, use domains instead. If you do use it, restart your application after every unhandled exception!
Do not use it as the node.js equivalent of On Error Resume Next
. An
unhandled exception means your application - and by extension node.js itself -
is in an undefined state. Blindly resuming means anything could happen.
Think of resuming as pulling the power cord when you are upgrading your system. Nine out of ten times nothing happens - but the 10th time, your system is bust.
You have been warned.
Signal Events#
Emitted when the processes receives a signal. See sigaction(2) for a list of standard POSIX signal names such as SIGINT, SIGHUP, etc.
Example of listening for SIGINT
:
// Start reading from stdin so we don't exit.
process.stdin.resume();
process.on('SIGINT', function() {
console.log('Got SIGINT. Press Control-D to exit.');
});
An easy way to send the SIGINT
signal is with Control-C
in most terminal
programs.
Note:
SIGUSR1
is reserved by node.js to start the debugger. It's possible to install a listener but that won't stop the debugger from starting.SIGTERM
andSIGINT
have default handlers on non-Windows platforms that resets the terminal mode before exiting with code128 + signal number
. If one of these signals has a listener installed, its default behaviour will be removed (node will no longer exit).SIGPIPE
is ignored by default, it can have a listener installed.SIGHUP
is generated on Windows when the console window is closed, and on other platforms under various similar conditions, see signal(7). It can have a listener installed, however node will be unconditionally terminated by Windows about 10 seconds later. On non-Windows platforms, the default behaviour ofSIGHUP
is to terminate node, but once a listener has been installed its default behaviour will be removed.SIGTERM
is not supported on Windows, it can be listened on.SIGINT
from the terminal is supported on all platforms, and can usually be generated withCTRL+C
(though this may be configurable). It is not generated when terminal raw mode is enabled.SIGBREAK
is delivered on Windows whenCTRL+BREAK
is pressed, on non-Windows platforms it can be listened on, but there is no way to send or generate it.SIGWINCH
is delivered when the console has been resized. On Windows, this will only happen on write to the console when the cursor is being moved, or when a readable tty is used in raw mode.SIGKILL
cannot have a listener installed, it will unconditionally terminate node on all platforms.SIGSTOP
cannot have a listener installed.
Note that Windows does not support sending Signals, but node offers some
emulation with process.kill()
, and child_process.kill()
:
- Sending signal 0
can be used to search for the existence of a process
- Sending SIGINT
, SIGTERM
, and SIGKILL
cause the unconditional exit of the
target process.
process.stdout#
A Writable Stream
to stdout
.
Example: the definition of console.log
console.log = function(d) {
process.stdout.write(d + '\n');
};
process.stderr
and process.stdout
are unlike other streams in Node in
that writes to them are usually blocking.
- They are blocking in the case that they refer to regular files or TTY file descriptors.
- In the case they refer to pipes:
- They are blocking in Linux/Unix.
- They are non-blocking like other streams in Windows.
To check if Node is being run in a TTY context, read the isTTY
property
on process.stderr
, process.stdout
, or process.stdin
:
$ node -p "Boolean(process.stdin.isTTY)"
true
$ echo "foo" | node -p "Boolean(process.stdin.isTTY)"
false
$ node -p "Boolean(process.stdout.isTTY)"
true
$ node -p "Boolean(process.stdout.isTTY)" | cat
false
See the tty docs for more information.
process.stderr#
A writable stream to stderr.
process.stderr
and process.stdout
are unlike other streams in Node in
that writes to them are usually blocking.
- They are blocking in the case that they refer to regular files or TTY file descriptors.
- In the case they refer to pipes:
- They are blocking in Linux/Unix.
- They are non-blocking like other streams in Windows.
process.stdin#
A Readable Stream
for stdin.
Example of opening standard input and listening for both events:
process.stdin.setEncoding('utf8');
process.stdin.on('readable', function() {
var chunk = process.stdin.read();
if (chunk !== null) {
process.stdout.write('data: ' + chunk);
}
});
process.stdin.on('end', function() {
process.stdout.write('end');
});
As a Stream, process.stdin
can also be used in "old" mode that is compatible
with scripts written for node prior v0.10.
For more information see
Stream compatibility.
In "old" Streams mode the stdin stream is paused by default, so one
must call process.stdin.resume()
to read from it. Note also that calling
process.stdin.resume()
itself would switch stream to "old" mode.
If you are starting a new project you should prefer a more recent "new" Streams mode over "old" one.
process.argv#
An array containing the command line arguments. The first element will be 'node', the second element will be the name of the JavaScript file. The next elements will be any additional command line arguments.
// print process.argv
process.argv.forEach(function(val, index, array) {
console.log(index + ': ' + val);
});
This will generate:
$ node process-2.js one two=three four
0: node
1: /Users/mjr/work/node/process-2.js
2: one
3: two=three
4: four
process.execPath#
This is the absolute pathname of the executable that started the process.
Example:
/usr/local/bin/node
process.execArgv#
This is the set of node-specific command line options from the
executable that started the process. These options do not show up in
process.argv
, and do not include the node executable, the name of
the script, or any options following the script name. These options
are useful in order to spawn child processes with the same execution
environment as the parent.
Example:
$ node --harmony script.js --version
results in process.execArgv:
['--harmony']
and process.argv:
['/usr/local/bin/node', 'script.js', '--version']
process.abort()#
This causes node to emit an abort. This will cause node to exit and generate a core file.
process.chdir(directory)#
Changes the current working directory of the process or throws an exception if that fails.
console.log('Starting directory: ' + process.cwd());
try {
process.chdir('/tmp');
console.log('New directory: ' + process.cwd());
}
catch (err) {
console.log('chdir: ' + err);
}
process.cwd()#
Returns the current working directory of the process.
console.log('Current directory: ' + process.cwd());
process.env#
An object containing the user environment. See environ(7).
An example of this object looks like:
{ TERM: 'xterm-256color',
SHELL: '/usr/local/bin/bash',
USER: 'maciej',
PATH: '~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin',
PWD: '/Users/maciej',
EDITOR: 'vim',
SHLVL: '1',
HOME: '/Users/maciej',
LOGNAME: 'maciej',
_: '/usr/local/bin/node' }
You can write to this object, but changes won't be reflected outside of your process. That means that the following won't work:
node -e 'process.env.foo = "bar"' && echo $foo
But this will:
process.env.foo = 'bar';
console.log(process.env.foo);
process.exit([code])#
Ends the process with the specified code
. If omitted, exit uses the
'success' code 0
.
To exit with a 'failure' code:
process.exit(1);
The shell that executed node should see the exit code as 1.
process.exitCode#
A number which will be the process exit code, when the process either
exits gracefully, or is exited via process.exit()
without specifying
a code.
Specifying a code to process.exit(code)
will override any previous
setting of process.exitCode
.
process.getgid()#
Note: this function is only available on POSIX platforms (i.e. not Windows, Android)
Gets the group identity of the process. (See getgid(2).) This is the numerical group id, not the group name.
if (process.getgid) {
console.log('Current gid: ' + process.getgid());
}
process.setgid(id)#
Note: this function is only available on POSIX platforms (i.e. not Windows, Android)
Sets the group identity of the process. (See setgid(2).) This accepts either a numerical ID or a groupname string. If a groupname is specified, this method blocks while resolving it to a numerical ID.
if (process.getgid && process.setgid) {
console.log('Current gid: ' + process.getgid());
try {
process.setgid(501);
console.log('New gid: ' + process.getgid());
}
catch (err) {
console.log('Failed to set gid: ' + err);
}
}
process.getuid()#
Note: this function is only available on POSIX platforms (i.e. not Windows, Android)
Gets the user identity of the process. (See getuid(2).) This is the numerical userid, not the username.
if (process.getuid) {
console.log('Current uid: ' + process.getuid());
}
process.setuid(id)#
Note: this function is only available on POSIX platforms (i.e. not Windows, Android)
Sets the user identity of the process. (See setuid(2).) This accepts either a numerical ID or a username string. If a username is specified, this method blocks while resolving it to a numerical ID.
if (process.getuid && process.setuid) {
console.log('Current uid: ' + process.getuid());
try {
process.setuid(501);
console.log('New uid: ' + process.getuid());
}
catch (err) {
console.log('Failed to set uid: ' + err);
}
}
process.getgroups()#
Note: this function is only available on POSIX platforms (i.e. not Windows, Android)
Returns an array with the supplementary group IDs. POSIX leaves it unspecified if the effective group ID is included but node.js ensures it always is.
process.setgroups(groups)#
Note: this function is only available on POSIX platforms (i.e. not Windows, Android)
Sets the supplementary group IDs. This is a privileged operation, meaning you need to be root or have the CAP_SETGID capability.
The list can contain group IDs, group names or both.
process.initgroups(user, extra_group)#
Note: this function is only available on POSIX platforms (i.e. not Windows, Android)
Reads /etc/group and initializes the group access list, using all groups of which the user is a member. This is a privileged operation, meaning you need to be root or have the CAP_SETGID capability.
user
is a user name or user ID. extra_group
is a group name or group ID.
Some care needs to be taken when dropping privileges. Example:
console.log(process.getgroups()); // [ 0 ]
process.initgroups('bnoordhuis', 1000); // switch user
console.log(process.getgroups()); // [ 27, 30, 46, 1000, 0 ]
process.setgid(1000); // drop root gid
console.log(process.getgroups()); // [ 27, 30, 46, 1000 ]
process.version#
A compiled-in property that exposes NODE_VERSION
.
console.log('Version: ' + process.version);
process.versions#
A property exposing version strings of node and its dependencies.
console.log(process.versions);
Will print something like:
{ http_parser: '1.0',
node: '0.10.4',
v8: '3.14.5.8',
ares: '1.9.0-DEV',
uv: '0.10.3',
zlib: '1.2.3',
modules: '11',
openssl: '1.0.1e' }
process.config#
An Object containing the JavaScript representation of the configure options
that were used to compile the current node executable. This is the same as
the "config.gypi" file that was produced when running the ./configure
script.
An example of the possible output looks like:
{ target_defaults:
{ cflags: [],
default_configuration: 'Release',
defines: [],
include_dirs: [],
libraries: [] },
variables:
{ host_arch: 'x64',
node_install_npm: 'true',
node_prefix: '',
node_shared_cares: 'false',
node_shared_http_parser: 'false',
node_shared_libuv: 'false',
node_shared_v8: 'false',
node_shared_zlib: 'false',
node_use_dtrace: 'false',
node_use_openssl: 'true',
node_shared_openssl: 'false',
strict_aliasing: 'true',
target_arch: 'x64',
v8_use_snapshot: 'true' } }
process.kill(pid, [signal])#
Send a signal to a process. pid
is the process id and signal
is the
string describing the signal to send. Signal names are strings like
'SIGINT' or 'SIGHUP'. If omitted, the signal will be 'SIGTERM'.
See Signal Events and kill(2) for more information.
Will throw an error if target does not exist, and as a special case, a signal of
0
can be used to test for the existence of a process.
Note that just because the name of this function is process.kill
, it is
really just a signal sender, like the kill
system call. The signal sent
may do something other than kill the target process.
Example of sending a signal to yourself:
process.on('SIGHUP', function() {
console.log('Got SIGHUP signal.');
});
setTimeout(function() {
console.log('Exiting.');
process.exit(0);
}, 100);
process.kill(process.pid, 'SIGHUP');
Note: When SIGUSR1 is received by Node.js it starts the debugger, see Signal Events.
process.pid#
The PID of the process.
console.log('This process is pid ' + process.pid);
process.title#
Getter/setter to set what is displayed in 'ps'.
When used as a setter, the maximum length is platform-specific and probably short.
On Linux and OS X, it's limited to the size of the binary name plus the length of the command line arguments because it overwrites the argv memory.
v0.8 allowed for longer process title strings by also overwriting the environ memory but that was potentially insecure/confusing in some (rather obscure) cases.
process.arch#
What processor architecture you're running on: 'arm'
, 'ia32'
, or 'x64'
.
console.log('This processor architecture is ' + process.arch);
process.platform#
What platform you're running on:
'darwin'
, 'freebsd'
, 'linux'
, 'sunos'
or 'win32'
console.log('This platform is ' + process.platform);
process.memoryUsage()#
Returns an object describing the memory usage of the Node process measured in bytes.
var util = require('util');
console.log(util.inspect(process.memoryUsage()));
This will generate:
{ rss: 4935680,
heapTotal: 1826816,
heapUsed: 650472 }
heapTotal
and heapUsed
refer to V8's memory usage.
process.nextTick(callback)#
callback
Function
Once the current event loop turn runs to completion, call the callback function.
This is not a simple alias to setTimeout(fn, 0)
, it's much more
efficient. It runs before any additional I/O events (including
timers) fire in subsequent ticks of the event loop.
console.log('start');
process.nextTick(function() {
console.log('nextTick callback');
});
console.log('scheduled');
// Output:
// start
// scheduled
// nextTick callback
This is important in developing APIs where you want to give the user the chance to assign event handlers after an object has been constructed, but before any I/O has occurred.
function MyThing(options) {
this.setupOptions(options);
process.nextTick(function() {
this.startDoingStuff();
}.bind(this));
}
var thing = new MyThing();
thing.getReadyForStuff();
// thing.startDoingStuff() gets called now, not before.
It is very important for APIs to be either 100% synchronous or 100% asynchronous. Consider this example:
// WARNING! DO NOT USE! BAD UNSAFE HAZARD!
function maybeSync(arg, cb) {
if (arg) {
cb();
return;
}
fs.stat('file', cb);
}
This API is hazardous. If you do this:
maybeSync(true, function() {
foo();
});
bar();
then it's not clear whether foo()
or bar()
will be called first.
This approach is much better:
function definitelyAsync(arg, cb) {
if (arg) {
process.nextTick(cb);
return;
}
fs.stat('file', cb);
}
Note: the nextTick queue is completely drained on each pass of the
event loop before additional I/O is processed. As a result,
recursively setting nextTick callbacks will block any I/O from
happening, just like a while(true);
loop.
process.umask([mask])#
Sets or reads the process's file mode creation mask. Child processes inherit
the mask from the parent process. Returns the old mask if mask
argument is
given, otherwise returns the current mask.
var oldmask, newmask = 0644;
oldmask = process.umask(newmask);
console.log('Changed umask from: ' + oldmask.toString(8) +
' to ' + newmask.toString(8));
process.uptime()#
Number of seconds Node has been running.
process.hrtime()#
Returns the current high-resolution real time in a [seconds, nanoseconds]
tuple Array. It is relative to an arbitrary time in the past. It is not
related to the time of day and therefore not subject to clock drift. The
primary use is for measuring performance between intervals.
You may pass in the result of a previous call to process.hrtime()
to get
a diff reading, useful for benchmarks and measuring intervals:
var time = process.hrtime();
// [ 1800216, 25 ]
setTimeout(function() {
var diff = process.hrtime(time);
// [ 1, 552 ]
console.log('benchmark took %d nanoseconds', diff[0] * 1e9 + diff[1]);
// benchmark took 1000000527 nanoseconds
}, 1000);
process.mainModule#
Alternate way to retrieve
require.main
.
The difference is that if the main module changes at runtime, require.main
might still refer to the original main module in modules that were required
before the change occurred. Generally it's safe to assume that the two refer
to the same module.
As with require.main
, it will be undefined
if there was no entry script.
util#
Stability: 4 - API Frozen
These functions are in the module 'util'
. Use require('util')
to
access them.
The util
module is primarily designed to support the needs of Node's
internal APIs. Many of these utilities are useful for your own
programs. If you find that these functions are lacking for your
purposes, however, you are encouraged to write your own utilities. We
are not interested in any future additions to the util
module that
are unnecessary for Node's internal functionality.
util.debuglog(section)#
section
String The section of the program to be debugged- Returns: Function The logging function
This is used to create a function which conditionally writes to stderr
based on the existence of a NODE_DEBUG
environment variable. If the
section
name appears in that environment variable, then the returned
function will be similar to console.error()
. If not, then the
returned function is a no-op.
For example:
var debuglog = util.debuglog('foo');
var bar = 123;
debuglog('hello from foo [%d]', bar);
If this program is run with NODE_DEBUG=foo
in the environment, then
it will output something like:
FOO 3245: hello from foo [123]
where 3245
is the process id. If it is not run with that
environment variable set, then it will not print anything.
You may separate multiple NODE_DEBUG
environment variables with a
comma. For example, NODE_DEBUG=fs,net,tls
.
util.format(format, [...])#
Returns a formatted string using the first argument as a printf
-like format.
The first argument is a string that contains zero or more placeholders. Each placeholder is replaced with the converted value from its corresponding argument. Supported placeholders are:
%s
- String.%d
- Number (both integer and float).%j
- JSON. Replaced with the string'[Circular]'
if the argumentcontains circular references.
%
- single percent sign ('%'
). This does not consume an argument.
If the placeholder does not have a corresponding argument, the placeholder is not replaced.
util.format('%s:%s', 'foo'); // 'foo:%s'
If there are more arguments than placeholders, the extra arguments are
converted to strings with util.inspect()
and these strings are concatenated,
delimited by a space.
util.format('%s:%s', 'foo', 'bar', 'baz'); // 'foo:bar baz'
If the first argument is not a format string then util.format()
returns
a string that is the concatenation of all its arguments separated by spaces.
Each argument is converted to a string with util.inspect()
.
util.format(1, 2, 3); // '1 2 3'
util.log(string)#
Output with timestamp on stdout
.
require('util').log('Timestamped message.');
util.inspect(object, [options])#
Return a string representation of object
, which is useful for debugging.
An optional options object may be passed that alters certain aspects of the formatted string:
showHidden
- iftrue
then the object's non-enumerable properties will be shown too. Defaults tofalse
.depth
- tellsinspect
how many times to recurse while formatting the object. This is useful for inspecting large complicated objects. Defaults to2
. To make it recurse indefinitely passnull
.colors
- iftrue
, then the output will be styled with ANSI color codes. Defaults tofalse
. Colors are customizable, see below.customInspect
- iffalse
, then custominspect(depth, opts)
functions defined on the objects being inspected won't be called. Defaults totrue
.
Example of inspecting all properties of the util
object:
var util = require('util');
console.log(util.inspect(util, { showHidden: true, depth: null }));
Values may supply their own custom inspect(depth, opts)
functions, when
called they receive the current depth in the recursive inspection, as well as
the options object passed to util.inspect()
.
Customizing util.inspect
colors#
Color output (if enabled) of util.inspect
is customizable globally
via util.inspect.styles
and util.inspect.colors
objects.
util.inspect.styles
is a map assigning each style a color
from util.inspect.colors
.
Highlighted styles and their default values are:
number
(yellow)
boolean
(yellow)
string
(green)
date
(magenta)
regexp
(red)
null
(bold)
undefined
(grey)
special
- only function at this time (cyan)
* name
(intentionally no styling)
Predefined color codes are: white
, grey
, black
, blue
, cyan
,
green
, magenta
, red
and yellow
.
There are also bold
, italic
, underline
and inverse
codes.
Custom inspect()
function on Objects#
Objects also may define their own inspect(depth)
function which util.inspect()
will invoke and use the result of when inspecting the object:
var util = require('util');
var obj = { name: 'nate' };
obj.inspect = function(depth) {
return '{' + this.name + '}';
};
util.inspect(obj);
// "{nate}"
You may also return another Object entirely, and the returned String will be
formatted according to the returned Object. This is similar to how
JSON.stringify()
works:
var obj = { foo: 'this will not show up in the inspect() output' };
obj.inspect = function(depth) {
return { bar: 'baz' };
};
util.inspect(obj);
// "{ bar: 'baz' }"
util.isArray(object)#
Internal alias for Array.isArray.
Returns true
if the given "object" is an Array
. false
otherwise.
var util = require('util');
util.isArray([])
// true
util.isArray(new Array)
// true
util.isArray({})
// false
util.isRegExp(object)#
Returns true
if the given "object" is a RegExp
. false
otherwise.
var util = require('util');
util.isRegExp(/some regexp/)
// true
util.isRegExp(new RegExp('another regexp'))
// true
util.isRegExp({})
// false
util.isDate(object)#
Returns true
if the given "object" is a Date
. false
otherwise.
var util = require('util');
util.isDate(new Date())
// true
util.isDate(Date())
// false (without 'new' returns a String)
util.isDate({})
// false
util.isError(object)#
Returns true
if the given "object" is an Error
. false
otherwise.
var util = require('util');
util.isError(new Error())
// true
util.isError(new TypeError())
// true
util.isError({ name: 'Error', message: 'an error occurred' })
// false
util.inherits(constructor, superConstructor)#
Inherit the prototype methods from one
constructor
into another. The prototype of constructor
will be set to a new
object created from superConstructor
.
As an additional convenience, superConstructor
will be accessible
through the constructor.super_
property.
var util = require("util");
var events = require("events");
function MyStream() {
events.EventEmitter.call(this);
}
util.inherits(MyStream, events.EventEmitter);
MyStream.prototype.write = function(data) {
this.emit("data", data);
}
var stream = new MyStream();
console.log(stream instanceof events.EventEmitter); // true
console.log(MyStream.super_ === events.EventEmitter); // true
stream.on("data", function(data) {
console.log('Received data: "' + data + '"');
})
stream.write("It works!"); // Received data: "It works!"
util.deprecate(function, string)#
Marks that a method should not be used any more.
exports.puts = exports.deprecate(function() {
for (var i = 0, len = arguments.length; i < len; ++i) {
process.stdout.write(arguments[i] + '\n');
}
}, 'util.puts: Use console.log instead')
It returns a modified function which warns once by default. If
--no-deprecation
is set then this function is a NO-OP. If
--throw-deprecation
is set then the application will throw an exception
if the deprecated API is used.
util.debug(string)#
Stability: 0 - Deprecated: use console.error() instead.
Deprecated predecessor of console.error
.
util.error([...])#
Stability: 0 - Deprecated: Use console.error() instead.
Deprecated predecessor of console.error
.
util.puts([...])#
Stability: 0 - Deprecated: Use console.log() instead.
Deprecated predecessor of console.log
.
util.print([...])#
Stability: 0 - Deprecated: Use console.log
instead.
Deprecated predecessor of console.log
.
util.pump(readableStream, writableStream, [callback])#
Stability: 0 - Deprecated: Use readableStream.pipe(writableStream)
Deprecated predecessor of stream.pipe()
.
Events#
Stability: 4 - API Frozen
Many objects in Node emit events: a net.Server
emits an event each time
a peer connects to it, a fs.readStream
emits an event when the file is
opened. All objects which emit events are instances of events.EventEmitter
.
You can access this module by doing: require("events");
Typically, event names are represented by a camel-cased string, however, there aren't any strict restrictions on that, as any string will be accepted.
Functions can then be attached to objects, to be executed when an event
is emitted. These functions are called listeners. Inside a listener
function, this
refers to the EventEmitter
that the listener was
attached to.
Class: events.EventEmitter#
To access the EventEmitter class, require('events').EventEmitter
.
When an EventEmitter
instance experiences an error, the typical action is
to emit an 'error'
event. Error events are treated as a special case in node.
If there is no listener for it, then the default action is to print a stack
trace and exit the program.
All EventEmitters emit the event 'newListener'
when new listeners are
added and 'removeListener'
when a listener is removed.
emitter.addListener(event, listener)#
emitter.on(event, listener)#
Adds a listener to the end of the listeners array for the specified event.
server.on('connection', function (stream) {
console.log('someone connected!');
});
Returns emitter, so calls can be chained.
emitter.once(event, listener)#
Adds a one time listener for the event. This listener is invoked only the next time the event is fired, after which it is removed.
server.once('connection', function (stream) {
console.log('Ah, we have our first user!');
});
Returns emitter, so calls can be chained.
emitter.removeListener(event, listener)#
Remove a listener from the listener array for the specified event. Caution: changes array indices in the listener array behind the listener.
var callback = function(stream) {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);
Returns emitter, so calls can be chained.
emitter.removeAllListeners([event])#
Removes all listeners, or those of the specified event. It's not a good idea to remove listeners that were added elsewhere in the code, especially when it's on an emitter that you didn't create (e.g. sockets or file streams).
Returns emitter, so calls can be chained.
emitter.setMaxListeners(n)#
By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default which helps finding memory leaks. Obviously not all Emitters should be limited to 10. This function allows that to be increased. Set to zero for unlimited.
Returns emitter, so calls can be chained.
EventEmitter.defaultMaxListeners#
emitter.setMaxListeners(n)
sets the maximum on a per-instance basis.
This class property lets you set it for all EventEmitter
instances,
current and future, effective immediately. Use with care.
Note that emitter.setMaxListeners(n)
still has precedence over
EventEmitter.defaultMaxListeners
.
emitter.listeners(event)#
Returns an array of listeners for the specified event.
server.on('connection', function (stream) {
console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection'))); // [ [Function] ]
emitter.emit(event, [arg1], [arg2], [...])#
Execute each of the listeners in order with the supplied arguments.
Returns true
if event had listeners, false
otherwise.
Class Method: EventEmitter.listenerCount(emitter, event)#
Return the number of listeners for a given event.
Event: 'newListener'#
event
String The event namelistener
Function The event handler function
This event is emitted any time someone adds a new listener. It is unspecified
if listener
is in the list returned by emitter.listeners(event)
.
Event: 'removeListener'#
event
String The event namelistener
Function The event handler function
This event is emitted any time someone removes a listener. It is unspecified
if listener
is in the list returned by emitter.listeners(event)
.
Domain#
Stability: 2 - Unstable
Domains provide a way to handle multiple different IO operations as a
single group. If any of the event emitters or callbacks registered to a
domain emit an error
event, or throw an error, then the domain object
will be notified, rather than losing the context of the error in the
process.on('uncaughtException')
handler, or causing the program to
exit immediately with an error code.
Warning: Don't Ignore Errors!#
Domain error handlers are not a substitute for closing down your process when an error occurs.
By the very nature of how throw
works in JavaScript, there is almost
never any way to safely "pick up where you left off", without leaking
references, or creating some other sort of undefined brittle state.
The safest way to respond to a thrown error is to shut down the process. Of course, in a normal web server, you might have many connections open, and it is not reasonable to abruptly shut those down because an error was triggered by someone else.
The better approach is send an error response to the request that triggered the error, while letting the others finish in their normal time, and stop listening for new requests in that worker.
In this way, domain
usage goes hand-in-hand with the cluster module,
since the master process can fork a new worker when a worker
encounters an error. For node programs that scale to multiple
machines, the terminating proxy or service registry can take note of
the failure, and react accordingly.
For example, this is not a good idea:
// XXX WARNING! BAD IDEA!
var d = require('domain').create();
d.on('error', function(er) {
// The error won't crash the process, but what it does is worse!
// Though we've prevented abrupt process restarting, we are leaking
// resources like crazy if this ever happens.
// This is no better than process.on('uncaughtException')!
console.log('error, but oh well', er.message);
});
d.run(function() {
require('http').createServer(function(req, res) {
handleRequest(req, res);
}).listen(PORT);
});
By using the context of a domain, and the resilience of separating our program into multiple worker processes, we can react more appropriately, and handle errors with much greater safety.
// Much better!
var cluster = require('cluster');
var PORT = +process.env.PORT || 1337;
if (cluster.isMaster) {
// In real life, you'd probably use more than just 2 workers,
// and perhaps not put the master and worker in the same file.
//
// You can also of course get a bit fancier about logging, and
// implement whatever custom logic you need to prevent DoS
// attacks and other bad behavior.
//
// See the options in the cluster documentation.
//
// The important thing is that the master does very little,
// increasing our resilience to unexpected errors.
cluster.fork();
cluster.fork();
cluster.on('disconnect', function(worker) {
console.error('disconnect!');
cluster.fork();
});
} else {
// the worker
//
// This is where we put our bugs!
var domain = require('domain');
// See the cluster documentation for more details about using
// worker processes to serve requests. How it works, caveats, etc.
var server = require('http').createServer(function(req, res) {
var d = domain.create();
d.on('error', function(er) {
console.error('error', er.stack);
// Note: we're in dangerous territory!
// By definition, something unexpected occurred,
// which we probably didn't want.
// Anything can happen now! Be very careful!
try {
// make sure we close down within 30 seconds
var killtimer = setTimeout(function() {
process.exit(1);
}, 30000);
// But don't keep the process open just for that!
killtimer.unref();
// stop taking new requests.
server.close();
// Let the master know we're dead. This will trigger a
// 'disconnect' in the cluster master, and then it will fork
// a new worker.
cluster.worker.disconnect();
// try to send an error to the request that triggered the problem
res.statusCode = 500;
res.setHeader('content-type', 'text/plain');
res.end('Oops, there was a problem!\n');
} catch (er2) {
// oh well, not much we can do at this point.
console.error('Error sending 500!', er2.stack);
}
});
// Because req and res were created before this domain existed,
// we need to explicitly add them.
// See the explanation of implicit vs explicit binding below.
d.add(req);
d.add(res);
// Now run the handler function in the domain.
d.run(function() {
handleRequest(req, res);
});
});
server.listen(PORT);
}
// This part isn't important. Just an example routing thing.
// You'd put your fancy application logic here.
function handleRequest(req, res) {
switch(req.url) {
case '/error':
// We do some async stuff, and then...
setTimeout(function() {
// Whoops!
flerb.bark();
});
break;
default:
res.end('ok');
}
}
Additions to Error objects#
Any time an Error object is routed through a domain, a few extra fields are added to it.
error.domain
The domain that first handled the error.error.domainEmitter
The event emitter that emitted an 'error' event with the error object.error.domainBound
The callback function which was bound to the domain, and passed an error as its first argument.error.domainThrown
A boolean indicating whether the error was thrown, emitted, or passed to a bound callback function.
Implicit Binding#
If domains are in use, then all new EventEmitter objects (including Stream objects, requests, responses, etc.) will be implicitly bound to the active domain at the time of their creation.
Additionally, callbacks passed to lowlevel event loop requests (such as to fs.open, or other callback-taking methods) will automatically be bound to the active domain. If they throw, then the domain will catch the error.
In order to prevent excessive memory usage, Domain objects themselves are not implicitly added as children of the active domain. If they were, then it would be too easy to prevent request and response objects from being properly garbage collected.
If you want to nest Domain objects as children of a parent Domain, then you must explicitly add them.
Implicit binding routes thrown errors and 'error'
events to the
Domain's error
event, but does not register the EventEmitter on the
Domain, so domain.dispose()
will not shut down the EventEmitter.
Implicit binding only takes care of thrown errors and 'error'
events.
Explicit Binding#
Sometimes, the domain in use is not the one that ought to be used for a specific event emitter. Or, the event emitter could have been created in the context of one domain, but ought to instead be bound to some other domain.
For example, there could be one domain in use for an HTTP server, but perhaps we would like to have a separate domain to use for each request.
That is possible via explicit binding.
For example:
// create a top-level domain for the server
var serverDomain = domain.create();
serverDomain.run(function() {
// server is created in the scope of serverDomain
http.createServer(function(req, res) {
// req and res are also created in the scope of serverDomain
// however, we'd prefer to have a separate domain for each request.
// create it first thing, and add req and res to it.
var reqd = domain.create();
reqd.add(req);
reqd.add(res);
reqd.on('error', function(er) {
console.error('Error', er, req.url);
try {
res.writeHead(500);
res.end('Error occurred, sorry.');
} catch (er) {
console.error('Error sending 500', er, req.url);
}
});
}).listen(1337);
});
domain.create()#
- return: Domain
Returns a new Domain object.
Class: Domain#
The Domain class encapsulates the functionality of routing errors and uncaught exceptions to the active Domain object.
Domain is a child class of EventEmitter. To handle the errors that it
catches, listen to its error
event.
domain.run(fn)#
fn
Function
Run the supplied function in the context of the domain, implicitly binding all event emitters, timers, and lowlevel requests that are created in that context.
This is the most basic way to use a domain.
Example:
var d = domain.create();
d.on('error', function(er) {
console.error('Caught error!', er);
});
d.run(function() {
process.nextTick(function() {
setTimeout(function() { // simulating some various async stuff
fs.open('non-existent file', 'r', function(er, fd) {
if (er) throw er;
// proceed...
});
}, 100);
});
});
In this example, the d.on('error')
handler will be triggered, rather
than crashing the program.
domain.members#
- Array
An array of timers and event emitters that have been explicitly added to the domain.
domain.add(emitter)#
emitter
EventEmitter | Timer emitter or timer to be added to the domain
Explicitly adds an emitter to the domain. If any event handlers called by
the emitter throw an error, or if the emitter emits an error
event, it
will be routed to the domain's error
event, just like with implicit
binding.
This also works with timers that are returned from setInterval
and
setTimeout
. If their callback function throws, it will be caught by
the domain 'error' handler.
If the Timer or EventEmitter was already bound to a domain, it is removed from that one, and bound to this one instead.
domain.remove(emitter)#
emitter
EventEmitter | Timer emitter or timer to be removed from the domain
The opposite of domain.add(emitter)
. Removes domain handling from the
specified emitter.
domain.bind(callback)#
callback
Function The callback function- return: Function The bound function
The returned function will be a wrapper around the supplied callback
function. When the returned function is called, any errors that are
thrown will be routed to the domain's error
event.
Example#
var d = domain.create();
function readSomeFile(filename, cb) {
fs.readFile(filename, 'utf8', d.bind(function(er, data) {
// if this throws, it will also be passed to the domain
return cb(er, data ? JSON.parse(data) : null);
}));
}
d.on('error', function(er) {
// an error occurred somewhere.
// if we throw it now, it will crash the program
// with the normal line number and stack message.
});
domain.intercept(callback)#
callback
Function The callback function- return: Function The intercepted function
This method is almost identical to domain.bind(callback)
. However, in
addition to catching thrown errors, it will also intercept Error
objects sent as the first argument to the function.
In this way, the common if (er) return callback(er);
pattern can be replaced
with a single error handler in a single place.
Example#
var d = domain.create();
function readSomeFile(filename, cb) {
fs.readFile(filename, 'utf8', d.intercept(function(data) {
// note, the first argument is never passed to the
// callback since it is assumed to be the 'Error' argument
// and thus intercepted by the domain.
// if this throws, it will also be passed to the domain
// so the error-handling logic can be moved to the 'error'
// event on the domain instead of being repeated throughout
// the program.
return cb(null, JSON.parse(data));
}));
}
d.on('error', function(er) {
// an error occurred somewhere.
// if we throw it now, it will crash the program
// with the normal line number and stack message.
});
domain.enter()#
The enter
method is plumbing used by the run
, bind
, and intercept
methods to set the active domain. It sets domain.active
and process.domain
to the domain, and implicitly pushes the domain onto the domain stack managed
by the domain module (see domain.exit()
for details on the domain stack). The
call to enter
delimits the beginning of a chain of asynchronous calls and I/O
operations bound to a domain.
Calling enter
changes only the active domain, and does not alter the domain
itself. Enter
and exit
can be called an arbitrary number of times on a
single domain.
If the domain on which enter
is called has been disposed, enter
will return
without setting the domain.
domain.exit()#
The exit
method exits the current domain, popping it off the domain stack.
Any time execution is going to switch to the context of a different chain of
asynchronous calls, it's important to ensure that the current domain is exited.
The call to exit
delimits either the end of or an interruption to the chain
of asynchronous calls and I/O operations bound to a domain.
If there are multiple, nested domains bound to the current execution context,
exit
will exit any domains nested within this domain.
Calling exit
changes only the active domain, and does not alter the domain
itself. Enter
and exit
can be called an arbitrary number of times on a
single domain.
If the domain on which exit
is called has been disposed, exit
will return
without exiting the domain.
domain.dispose()#
Stability: 0 - Deprecated. Please recover from failed IO actions explicitly via error event handlers set on the domain.
Once dispose
has been called, the domain will no longer be used by callbacks
bound into the domain via run
, bind
, or intercept
, and a dispose
event
is emitted.
Buffer#
Stability: 3 - Stable
Pure JavaScript is Unicode friendly but not nice to binary data. When dealing with TCP streams or the file system, it's necessary to handle octet streams. Node has several strategies for manipulating, creating, and consuming octet streams.
Raw data is stored in instances of the Buffer
class. A Buffer
is similar
to an array of integers but corresponds to a raw memory allocation outside
the V8 heap. A Buffer
cannot be resized.
The Buffer
class is a global, making it very rare that one would need
to ever require('buffer')
.
Converting between Buffers and JavaScript string objects requires an explicit encoding method. Here are the different string encodings.
'ascii'
- for 7 bit ASCII data only. This encoding method is very fast, and will strip the high bit if set.'utf8'
- Multibyte encoded Unicode characters. Many web pages and other document formats use UTF-8.'utf16le'
- 2 or 4 bytes, little endian encoded Unicode characters. Surrogate pairs (U+10000 to U+10FFFF) are supported.'ucs2'
- Alias of'utf16le'
.'base64'
- Base64 string encoding.'binary'
- A way of encoding raw binary data into strings by using only the first 8 bits of each character. This encoding method is deprecated and should be avoided in favor ofBuffer
objects where possible. This encoding will be removed in future versions of Node.'hex'
- Encode each byte as two hexadecimal characters.
Creating a typed array from a Buffer
works with the following caveats:
The buffer's memory is copied, not shared.
The buffer's memory is interpreted as an array, not a byte array. That is,
new Uint32Array(new Buffer([1,2,3,4]))
creates a 4-elementUint32Array
with elements[1,2,3,4]
, not anUint32Array
with a single element[0x1020304]
or[0x4030201]
.
NOTE: Node.js v0.8 simply retained a reference to the buffer in array.buffer
instead of cloning it.
While more efficient, it introduces subtle incompatibilities with the typed
arrays specification. ArrayBuffer#slice()
makes a copy of the slice while
Buffer#slice()
creates a view.
Class: Buffer#
The Buffer class is a global type for dealing with binary data directly. It can be constructed in a variety of ways.
new Buffer(size)#
size
Number
Allocates a new buffer of size
octets. Note, size
must be no more than
kMaxLength. Otherwise, a RangeError
will be thrown here.
new Buffer(array)#
array
Array
Allocates a new buffer using an array
of octets.
new Buffer(str, [encoding])#
str
String - string to encode.encoding
String - encoding to use, Optional.
Allocates a new buffer containing the given str
.
encoding
defaults to 'utf8'
.
Class Method: Buffer.isEncoding(encoding)#
encoding
String The encoding string to test
Returns true if the encoding
is a valid encoding argument, or false
otherwise.
Class Method: Buffer.isBuffer(obj)#
obj
Object- Return: Boolean
Tests if obj
is a Buffer
.
Class Method: Buffer.byteLength(string, [encoding])#
string
Stringencoding
String, Optional, Default: 'utf8'- Return: Number
Gives the actual byte length of a string. encoding
defaults to 'utf8'
.
This is not the same as String.prototype.length
since that returns the
number of characters in a string.
Example:
str = '\u00bd + \u00bc = \u00be';
console.log(str + ": " + str.length + " characters, " +
Buffer.byteLength(str, 'utf8') + " bytes");
// ½ + ¼ = ¾: 9 characters, 12 bytes
Class Method: Buffer.concat(list, [totalLength])#
list
Array List of Buffer objects to concattotalLength
Number Total length of the buffers when concatenated
Returns a buffer which is the result of concatenating all the buffers in the list together.
If the list has no items, or if the totalLength is 0, then it returns a zero-length buffer.
If the list has exactly one item, then the first item of the list is returned.
If the list has more than one item, then a new Buffer is created.
If totalLength is not provided, it is read from the buffers in the list. However, this adds an additional loop to the function, so it is faster to provide the length explicitly.
Class Method: Buffer.compare(buf1, buf2)#
buf1
Bufferbuf2
Buffer
The same as buf1.compare(buf2)
. Useful
for sorting an Array of Buffers:
var arr = [Buffer('1234'), Buffer('0123')];
arr.sort(Buffer.compare);
buf.length#
- Number
The size of the buffer in bytes. Note that this is not necessarily the size
of the contents. length
refers to the amount of memory allocated for the
buffer object. It does not change when the contents of the buffer are changed.
buf = new Buffer(1234);
console.log(buf.length);
buf.write("some string", 0, "ascii");
console.log(buf.length);
// 1234
// 1234
buf.write(string, [offset], [length], [encoding])#
string
String - data to be written to bufferoffset
Number, Optional, Default: 0length
Number, Optional, Default:buffer.length - offset
encoding
String, Optional, Default: 'utf8'
Writes string
to the buffer at offset
using the given encoding.
offset
defaults to 0
, encoding
defaults to 'utf8'
. length
is
the number of bytes to write. Returns number of octets written. If buffer
did
not contain enough space to fit the entire string, it will write a partial
amount of the string. length
defaults to buffer.length - offset
.
The method will not write partial characters.
buf = new Buffer(256);
len = buf.write('\u00bd + \u00bc = \u00be', 0);
console.log(len + " bytes: " + buf.toString('utf8', 0, len));
buf.toString([encoding], [start], [end])#
encoding
String, Optional, Default: 'utf8'start
Number, Optional, Default: 0end
Number, Optional, Default:buffer.length
Decodes and returns a string from buffer data encoded with encoding
(defaults to 'utf8'
) beginning at start
(defaults to 0
) and ending at
end
(defaults to buffer.length
).
See buffer.write()
example, above.
buf.toJSON()#
Returns a JSON-representation of the Buffer instance. JSON.stringify
implicitly calls this function when stringifying a Buffer instance.
Example:
var buf = new Buffer('test');
var json = JSON.stringify(buf);
console.log(json);
// '{"type":"Buffer","data":[116,101,115,116]}'
var copy = JSON.parse(json, function(key, value) {
return value && value.type === 'Buffer'
? new Buffer(value.data)
: value;
});
console.log(copy);
// <Buffer 74 65 73 74>
buf[index]#
Get and set the octet at index
. The values refer to individual bytes,
so the legal range is between 0x00
and 0xFF
hex or 0
and 255
.
Example: copy an ASCII string into a buffer, one byte at a time:
str = "node.js";
buf = new Buffer(str.length);
for (var i = 0; i < str.length ; i++) {
buf[i] = str.charCodeAt(i);
}
console.log(buf);
// node.js
buf.equals(otherBuffer)#
otherBuffer
Buffer
Returns a boolean of whether this
and otherBuffer
have the same
bytes.
buf.compare(otherBuffer)#
otherBuffer
Buffer
Returns a number indicating whether this
comes before or after or is
the same as the otherBuffer
in sort order.
buf.copy(targetBuffer, [targetStart], [sourceStart], [sourceEnd])#
targetBuffer
Buffer object - Buffer to copy intotargetStart
Number, Optional, Default: 0sourceStart
Number, Optional, Default: 0sourceEnd
Number, Optional, Default:buffer.length
Does copy between buffers. The source and target regions can be overlapped.
targetStart
and sourceStart
default to 0
.
sourceEnd
defaults to buffer.length
.
All values passed that are undefined
/NaN
or are out of bounds are set equal
to their respective defaults.
Example: build two Buffers, then copy buf1
from byte 16 through byte 19
into buf2
, starting at the 8th byte in buf2
.
buf1 = new Buffer(26);
buf2 = new Buffer(26);
for (var i = 0 ; i < 26 ; i++) {
buf1[i] = i + 97; // 97 is ASCII a
buf2[i] = 33; // ASCII !
}
buf1.copy(buf2, 8, 16, 20);
console.log(buf2.toString('ascii', 0, 25));
// !!!!!!!!qrst!!!!!!!!!!!!!
buf.slice([start], [end])#
start
Number, Optional, Default: 0end
Number, Optional, Default:buffer.length
Returns a new buffer which references the same memory as the old, but offset
and cropped by the start
(defaults to 0
) and end
(defaults to
buffer.length
) indexes. Negative indexes start from the end of the buffer.
Modifying the new buffer slice will modify memory in the original buffer!
Example: build a Buffer with the ASCII alphabet, take a slice, then modify one byte from the original Buffer.
var buf1 = new Buffer(26);
for (var i = 0 ; i < 26 ; i++) {
buf1[i] = i + 97; // 97 is ASCII a
}
var buf2 = buf1.slice(0, 3);
console.log(buf2.toString('ascii', 0, buf2.length));
buf1[0] = 33;
console.log(buf2.toString('ascii', 0, buf2.length));
// abc
// !bc
buf.readUInt8(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads an unsigned 8 bit integer from the buffer at the specified offset.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(4);
buf[0] = 0x3;
buf[1] = 0x4;
buf[2] = 0x23;
buf[3] = 0x42;
for (ii = 0; ii < buf.length; ii++) {
console.log(buf.readUInt8(ii));
}
// 0x3
// 0x4
// 0x23
// 0x42
buf.readUInt16LE(offset, [noAssert])#
buf.readUInt16BE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads an unsigned 16 bit integer from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(4);
buf[0] = 0x3;
buf[1] = 0x4;
buf[2] = 0x23;
buf[3] = 0x42;
console.log(buf.readUInt16BE(0));
console.log(buf.readUInt16LE(0));
console.log(buf.readUInt16BE(1));
console.log(buf.readUInt16LE(1));
console.log(buf.readUInt16BE(2));
console.log(buf.readUInt16LE(2));
// 0x0304
// 0x0403
// 0x0423
// 0x2304
// 0x2342
// 0x4223
buf.readUInt32LE(offset, [noAssert])#
buf.readUInt32BE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads an unsigned 32 bit integer from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(4);
buf[0] = 0x3;
buf[1] = 0x4;
buf[2] = 0x23;
buf[3] = 0x42;
console.log(buf.readUInt32BE(0));
console.log(buf.readUInt32LE(0));
// 0x03042342
// 0x42230403
buf.readInt8(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a signed 8 bit integer from the buffer at the specified offset.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Works as buffer.readUInt8
, except buffer contents are treated as two's
complement signed values.
buf.readInt16LE(offset, [noAssert])#
buf.readInt16BE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a signed 16 bit integer from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Works as buffer.readUInt16*
, except buffer contents are treated as two's
complement signed values.
buf.readInt32LE(offset, [noAssert])#
buf.readInt32BE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a signed 32 bit integer from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Works as buffer.readUInt32*
, except buffer contents are treated as two's
complement signed values.
buf.readFloatLE(offset, [noAssert])#
buf.readFloatBE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a 32 bit float from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(4);
buf[0] = 0x00;
buf[1] = 0x00;
buf[2] = 0x80;
buf[3] = 0x3f;
console.log(buf.readFloatLE(0));
// 0x01
buf.readDoubleLE(offset, [noAssert])#
buf.readDoubleBE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a 64 bit double from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(8);
buf[0] = 0x55;
buf[1] = 0x55;
buf[2] = 0x55;
buf[3] = 0x55;
buf[4] = 0x55;
buf[5] = 0x55;
buf[6] = 0xd5;
buf[7] = 0x3f;
console.log(buf.readDoubleLE(0));
// 0.3333333333333333
buf.writeUInt8(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset. Note, value
must be a
valid unsigned 8 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(4);
buf.writeUInt8(0x3, 0);
buf.writeUInt8(0x4, 1);
buf.writeUInt8(0x23, 2);
buf.writeUInt8(0x42, 3);
console.log(buf);
// <Buffer 03 04 23 42>
buf.writeUInt16LE(value, offset, [noAssert])#
buf.writeUInt16BE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid unsigned 16 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(4);
buf.writeUInt16BE(0xdead, 0);
buf.writeUInt16BE(0xbeef, 2);
console.log(buf);
buf.writeUInt16LE(0xdead, 0);
buf.writeUInt16LE(0xbeef, 2);
console.log(buf);
// <Buffer de ad be ef>
// <Buffer ad de ef be>
buf.writeUInt32LE(value, offset, [noAssert])#
buf.writeUInt32BE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid unsigned 32 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(4);
buf.writeUInt32BE(0xfeedface, 0);
console.log(buf);
buf.writeUInt32LE(0xfeedface, 0);
console.log(buf);
// <Buffer fe ed fa ce>
// <Buffer ce fa ed fe>
buf.writeInt8(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset. Note, value
must be a
valid signed 8 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Works as buffer.writeUInt8
, except value is written out as a two's complement
signed integer into buffer
.
buf.writeInt16LE(value, offset, [noAssert])#
buf.writeInt16BE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid signed 16 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Works as buffer.writeUInt16*
, except value is written out as a two's
complement signed integer into buffer
.
buf.writeInt32LE(value, offset, [noAssert])#
buf.writeInt32BE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid signed 32 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Works as buffer.writeUInt32*
, except value is written out as a two's
complement signed integer into buffer
.
buf.writeFloatLE(value, offset, [noAssert])#
buf.writeFloatBE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, behavior is unspecified if value
is not a 32 bit float.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(4);
buf.writeFloatBE(0xcafebabe, 0);
console.log(buf);
buf.writeFloatLE(0xcafebabe, 0);
console.log(buf);
// <Buffer 4f 4a fe bb>
// <Buffer bb fe 4a 4f>
buf.writeDoubleLE(value, offset, [noAssert])#
buf.writeDoubleBE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid 64 bit double.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(8);
buf.writeDoubleBE(0xdeadbeefcafebabe, 0);
console.log(buf);
buf.writeDoubleLE(0xdeadbeefcafebabe, 0);
console.log(buf);
// <Buffer 43 eb d5 b7 dd f9 5f d7>
// <Buffer d7 5f f9 dd b7 d5 eb 43>
buf.fill(value, [offset], [end])#
value
offset
Number, Optionalend
Number, Optional
Fills the buffer with the specified value. If the offset
(defaults to 0
)
and end
(defaults to buffer.length
) are not given it will fill the entire
buffer.
var b = new Buffer(50);
b.fill("h");
buffer.INSPECT_MAX_BYTES#
- Number, Default: 50
How many bytes will be returned when buffer.inspect()
is called. This can
be overridden by user modules.
Note that this is a property on the buffer module returned by
require('buffer')
, not on the Buffer global, or a buffer instance.
Class: SlowBuffer#
Returns an un-pooled Buffer
.
In order to avoid the garbage collection overhead of creating many individually
allocated Buffers, by default allocations under 4KB are sliced from a single
larger allocated object. This approach improves both performance and memory
usage since v8 does not need to track and cleanup as many Persistent
objects.
In the case where a developer may need to retain a small chunk of memory from a pool for an indeterminate amount of time it may be appropriate to create an un-pooled Buffer instance using SlowBuffer and copy out the relevant bits.
// need to keep around a few small chunks of memory
var store = [];
socket.on('readable', function() {
var data = socket.read();
// allocate for retained data
var sb = new SlowBuffer(10);
// copy the data into the new allocation
data.copy(sb, 0, 0, 10);
store.push(sb);
});
Though this should used sparingly and only be a last resort after a developer has actively observed undue memory retention in their applications.
Stream#
Stability: 2 - Unstable
A stream is an abstract interface implemented by various objects in Node. For example a request to an HTTP server is a stream, as is stdout. Streams are readable, writable, or both. All streams are instances of EventEmitter
You can load the Stream base classes by doing require('stream')
.
There are base classes provided for Readable streams, Writable
streams, Duplex streams, and Transform streams.
This document is split up into 3 sections. The first explains the parts of the API that you need to be aware of to use streams in your programs. If you never implement a streaming API yourself, you can stop there.
The second section explains the parts of the API that you need to use if you implement your own custom streams yourself. The API is designed to make this easy for you to do.
The third section goes into more depth about how streams work, including some of the internal mechanisms and functions that you should probably not modify unless you definitely know what you are doing.
API for Stream Consumers#
Streams can be either Readable, Writable, or both (Duplex).
All streams are EventEmitters, but they also have other custom methods and properties depending on whether they are Readable, Writable, or Duplex.
If a stream is both Readable and Writable, then it implements all of the methods and events below. So, a Duplex or Transform stream is fully described by this API, though their implementation may be somewhat different.
It is not necessary to implement Stream interfaces in order to consume streams in your programs. If you are implementing streaming interfaces in your own program, please also refer to API for Stream Implementors below.
Almost all Node programs, no matter how simple, use Streams in some way. Here is an example of using Streams in a Node program:
var http = require('http');
var server = http.createServer(function (req, res) {
// req is an http.IncomingMessage, which is a Readable Stream
// res is an http.ServerResponse, which is a Writable Stream
var body = '';
// we want to get the data as utf8 strings
// If you don't set an encoding, then you'll get Buffer objects
req.setEncoding('utf8');
// Readable streams emit 'data' events once a listener is added
req.on('data', function (chunk) {
body += chunk;
})
// the end event tells you that you have entire body
req.on('end', function () {
try {
var data = JSON.parse(body);
} catch (er) {
// uh oh! bad json!
res.statusCode = 400;
return res.end('error: ' + er.message);
}
// write back something interesting to the user:
res.write(typeof data);
res.end();
})
})
server.listen(1337);
// $ curl localhost:1337 -d '{}'
// object
// $ curl localhost:1337 -d '"foo"'
// string
// $ curl localhost:1337 -d 'not json'
// error: Unexpected token o
Class: stream.Readable#
The Readable stream interface is the abstraction for a source of data that you are reading from. In other words, data comes out of a Readable stream.
A Readable stream will not start emitting data until you indicate that you are ready to receive it.
Readable streams have two "modes": a flowing mode and a paused
mode. When in flowing mode, data is read from the underlying system
and provided to your program as fast as possible. In paused mode, you
must explicitly call stream.read()
to get chunks of data out.
Streams start out in paused mode.
Note: If no data event handlers are attached, and there are no
pipe()
destinations, and the stream is switched into flowing
mode, then data will be lost.
You can switch to flowing mode by doing any of the following:
- Adding a
'data'
event handler to listen for data. - Calling the
resume()
method to explicitly open the flow. - Calling the
pipe()
method to send the data to a Writable.
You can switch back to paused mode by doing either of the following:
- If there are no pipe destinations, by calling the
pause()
method. - If there are pipe destinations, by removing any
'data'
event handlers, and removing all pipe destinations by calling theunpipe()
method.
Note that, for backwards compatibility reasons, removing 'data'
event handlers will not automatically pause the stream. Also, if
there are piped destinations, then calling pause()
will not
guarantee that the stream will remain paused once those
destinations drain and ask for more data.
Examples of readable streams include:
- http responses, on the client
- http requests, on the server
- fs read streams
- zlib streams
- crypto streams
- tcp sockets
- child process stdout and stderr
- process.stdin
Event: 'readable'#
When a chunk of data can be read from the stream, it will emit a
'readable'
event.
In some cases, listening for a 'readable'
event will cause some data
to be read into the internal buffer from the underlying system, if it
hadn't already.
var readable = getReadableStreamSomehow();
readable.on('readable', function() {
// there is some data to read now
})
Once the internal buffer is drained, a readable
event will fire
again when more data is available.
Event: 'data'#
chunk
Buffer | String The chunk of data.
Attaching a data
event listener to a stream that has not been
explicitly paused will switch the stream into flowing mode. Data will
then be passed as soon as it is available.
If you just want to get all the data out of the stream as fast as possible, this is the best way to do so.
var readable = getReadableStreamSomehow();
readable.on('data', function(chunk) {
console.log('got %d bytes of data', chunk.length);
})
Event: 'end'#
This event fires when there will be no more data to read.
Note that the end
event will not fire unless the data is
completely consumed. This can be done by switching into flowing mode,
or by calling read()
repeatedly until you get to the end.
var readable = getReadableStreamSomehow();
readable.on('data', function(chunk) {
console.log('got %d bytes of data', chunk.length);
})
readable.on('end', function() {
console.log('there will be no more data.');
});
Event: 'close'#
Emitted when the underlying resource (for example, the backing file descriptor) has been closed. Not all streams will emit this.
Event: 'error'#
- Error Object
Emitted if there was an error receiving data.
readable.read([size])#
size
Number Optional argument to specify how much data to read.- Return String | Buffer | null
The read()
method pulls some data out of the internal buffer and
returns it. If there is no data available, then it will return
null
.
If you pass in a size
argument, then it will return that many
bytes. If size
bytes are not available, then it will return null
.
If you do not specify a size
argument, then it will return all the
data in the internal buffer.
This method should only be called in paused mode. In flowing mode, this method is called automatically until the internal buffer is drained.
var readable = getReadableStreamSomehow();
readable.on('readable', function() {
var chunk;
while (null !== (chunk = readable.read())) {
console.log('got %d bytes of data', chunk.length);
}
});
If this method returns a data chunk, then it will also trigger the
emission of a 'data'
event.
readable.setEncoding(encoding)#
encoding
String The encoding to use.- Return:
this
Call this function to cause the stream to return strings of the
specified encoding instead of Buffer objects. For example, if you do
readable.setEncoding('utf8')
, then the output data will be
interpreted as UTF-8 data, and returned as strings. If you do
readable.setEncoding('hex')
, then the data will be encoded in
hexadecimal string format.
This properly handles multi-byte characters that would otherwise be
potentially mangled if you simply pulled the Buffers directly and
called buf.toString(encoding)
on them. If you want to read the data
as strings, always use this method.
var readable = getReadableStreamSomehow();
readable.setEncoding('utf8');
readable.on('data', function(chunk) {
assert.equal(typeof chunk, 'string');
console.log('got %d characters of string data', chunk.length);
})
readable.resume()#
- Return:
this
This method will cause the readable stream to resume emitting data
events.
This method will switch the stream into flowing mode. If you do not
want to consume the data from a stream, but you do want to get to
its end
event, you can call readable.resume()
to open the flow of
data.
var readable = getReadableStreamSomehow();
readable.resume();
readable.on('end', function(chunk) {
console.log('got to the end, but did not read anything');
})
readable.pause()#
- Return:
this
This method will cause a stream in flowing mode to stop emitting
data
events, switching out of flowing mode. Any data that becomes
available will remain in the internal buffer.
var readable = getReadableStreamSomehow();
readable.on('data', function(chunk) {
console.log('got %d bytes of data', chunk.length);
readable.pause();
console.log('there will be no more data for 1 second');
setTimeout(function() {
console.log('now data will start flowing again');
readable.resume();
}, 1000);
})
readable.isPaused()#
- Return:
Boolean
This method returns whether or not the readable
has been explicitly
paused by client code (using readable.pause()
without a corresponding
readable.resume()
).
var readable = new stream.Readable
readable.isPaused() // === false
readable.pause()
readable.isPaused() // === true
readable.resume()
readable.isPaused() // === false
readable.pipe(destination, [options])#
destination
Writable Stream The destination for writing dataoptions
Object Pipe optionsend
Boolean End the writer when the reader ends. Default =true
This method pulls all the data out of a readable stream, and writes it to the supplied destination, automatically managing the flow so that the destination is not overwhelmed by a fast readable stream.
Multiple destinations can be piped to safely.
var readable = getReadableStreamSomehow();
var writable = fs.createWriteStream('file.txt');
// All the data from readable goes into 'file.txt'
readable.pipe(writable);
This function returns the destination stream, so you can set up pipe chains like so:
var r = fs.createReadStream('file.txt');
var z = zlib.createGzip();
var w = fs.createWriteStream('file.txt.gz');
r.pipe(z).pipe(w);
For example, emulating the Unix cat
command:
process.stdin.pipe(process.stdout);
By default end()
is called on the destination when the source stream
emits end
, so that destination
is no longer writable. Pass { end:
false }
as options
to keep the destination stream open.
This keeps writer
open so that "Goodbye" can be written at the
end.
reader.pipe(writer, { end: false });
reader.on('end', function() {
writer.end('Goodbye\n');
});
Note that process.stderr
and process.stdout
are never closed until
the process exits, regardless of the specified options.
readable.unpipe([destination])#
destination
Writable Stream Optional specific stream to unpipe
This method will remove the hooks set up for a previous pipe()
call.
If the destination is not specified, then all pipes are removed.
If the destination is specified, but no pipe is set up for it, then this is a no-op.
var readable = getReadableStreamSomehow();
var writable = fs.createWriteStream('file.txt');
// All the data from readable goes into 'file.txt',
// but only for the first second
readable.pipe(writable);
setTimeout(function() {
console.log('stop writing to file.txt');
readable.unpipe(writable);
console.log('manually close the file stream');
writable.end();
}, 1000);
readable.unshift(chunk)#
chunk
Buffer | String Chunk of data to unshift onto the read queue
This is useful in certain cases where a stream is being consumed by a parser, which needs to "un-consume" some data that it has optimistically pulled out of the source, so that the stream can be passed on to some other party.
If you find that you must often call stream.unshift(chunk)
in your
programs, consider implementing a Transform stream instead. (See API
for Stream Implementors, below.)
// Pull off a header delimited by \n\n
// use unshift() if we get too much
// Call the callback with (error, header, stream)
var StringDecoder = require('string_decoder').StringDecoder;
function parseHeader(stream, callback) {
stream.on('error', callback);
stream.on('readable', onReadable);
var decoder = new StringDecoder('utf8');
var header = '';
function onReadable() {
var chunk;
while (null !== (chunk = stream.read())) {
var str = decoder.write(chunk);
if (str.match(/\n\n/)) {
// found the header boundary
var split = str.split(/\n\n/);
header += split.shift();
var remaining = split.join('\n\n');
var buf = new Buffer(remaining, 'utf8');
if (buf.length)
stream.unshift(buf);
stream.removeListener('error', callback);
stream.removeListener('readable', onReadable);
// now the body of the message can be read from the stream.
callback(null, header, stream);
} else {
// still reading the header.
header += str;
}
}
}
}
readable.wrap(stream)#
stream
Stream An "old style" readable stream
Versions of Node prior to v0.10 had streams that did not implement the entire Streams API as it is today. (See "Compatibility" below for more information.)
If you are using an older Node library that emits 'data'
events and
has a pause()
method that is advisory only, then you can use the
wrap()
method to create a Readable stream that uses the old stream
as its data source.
You will very rarely ever need to call this function, but it exists as a convenience for interacting with old Node programs and libraries.
For example:
var OldReader = require('./old-api-module.js').OldReader;
var oreader = new OldReader;
var Readable = require('stream').Readable;
var myReader = new Readable().wrap(oreader);
myReader.on('readable', function() {
myReader.read(); // etc.
});
Class: stream.Writable#
The Writable stream interface is an abstraction for a destination that you are writing data to.
Examples of writable streams include:
- http requests, on the client
- http responses, on the server
- fs write streams
- zlib streams
- crypto streams
- tcp sockets
- child process stdin
- process.stdout, process.stderr
writable.write(chunk, [encoding], [callback])#
chunk
String | Buffer The data to writeencoding
String The encoding, ifchunk
is a Stringcallback
Function Callback for when this chunk of data is flushed- Returns: Boolean True if the data was handled completely.
This method writes some data to the underlying system, and calls the supplied callback once the data has been fully handled.
The return value indicates if you should continue writing right now.
If the data had to be buffered internally, then it will return
false
. Otherwise, it will return true
.
This return value is strictly advisory. You MAY continue to write,
even if it returns false
. However, writes will be buffered in
memory, so it is best not to do this excessively. Instead, wait for
the drain
event before writing more data.
Event: 'drain'#
If a writable.write(chunk)
call returns false, then the drain
event will indicate when it is appropriate to begin writing more data
to the stream.
// Write the data to the supplied writable stream 1MM times.
// Be attentive to back-pressure.
function writeOneMillionTimes(writer, data, encoding, callback) {
var i = 1000000;
write();
function write() {
var ok = true;
do {
i -= 1;
if (i === 0) {
// last time!
writer.write(data, encoding, callback);
} else {
// see if we should continue, or wait
// don't pass the callback, because we're not done yet.
ok = writer.write(data, encoding);
}
} while (i > 0 && ok);
if (i > 0) {
// had to stop early!
// write some more once it drains
writer.once('drain', write);
}
}
}
writable.cork()#
Forces buffering of all writes.
Buffered data will be flushed either at .uncork()
or at .end()
call.
writable.uncork()#
Flush all data, buffered since .cork()
call.
writable.end([chunk], [encoding], [callback])#
chunk
String | Buffer Optional data to writeencoding
String The encoding, ifchunk
is a Stringcallback
Function Optional callback for when the stream is finished
Call this method when no more data will be written to the stream. If
supplied, the callback is attached as a listener on the finish
event.
Calling write()
after calling end()
will raise an error.
// write 'hello, ' and then end with 'world!'
http.createServer(function (req, res) {
res.write('hello, ');
res.end('world!');
// writing more now is not allowed!
});
Event: 'finish'#
When the end()
method has been called, and all data has been flushed
to the underlying system, this event is emitted.
var writer = getWritableStreamSomehow();
for (var i = 0; i < 100; i ++) {
writer.write('hello, #' + i + '!\n');
}
writer.end('this is the end\n');
writer.on('finish', function() {
console.error('all writes are now complete.');
});
Event: 'pipe'#
src
Readable Stream source stream that is piping to this writable
This is emitted whenever the pipe()
method is called on a readable
stream, adding this writable to its set of destinations.
var writer = getWritableStreamSomehow();
var reader = getReadableStreamSomehow();
writer.on('pipe', function(src) {
console.error('something is piping into the writer');
assert.equal(src, reader);
});
reader.pipe(writer);
Event: 'unpipe'#
This is emitted whenever the unpipe()
method is called on a
readable stream, removing this writable from its set of destinations.
var writer = getWritableStreamSomehow();
var reader = getReadableStreamSomehow();
writer.on('unpipe', function(src) {
console.error('something has stopped piping into the writer');
assert.equal(src, reader);
});
reader.pipe(writer);
reader.unpipe(writer);
Event: 'error'#
- Error object
Emitted if there was an error when writing or piping data.
Class: stream.Duplex#
Duplex streams are streams that implement both the Readable and Writable interfaces. See above for usage.
Examples of Duplex streams include:
Class: stream.Transform#
Transform streams are Duplex streams where the output is in some way computed from the input. They implement both the Readable and Writable interfaces. See above for usage.
Examples of Transform streams include:
API for Stream Implementors#
To implement any sort of stream, the pattern is the same:
- Extend the appropriate parent class in your own subclass. (The
util.inherits
method is particularly helpful for this.) - Call the appropriate parent class constructor in your constructor, to be sure that the internal mechanisms are set up properly.
- Implement one or more specific methods, as detailed below.
The class to extend and the method(s) to implement depend on the sort of stream class you are writing:
Use-case |
Class |
Method(s) to implement |
---|---|---|
Reading only |
||
Writing only |
||
Reading and writing |
||
Operate on written data, then read the result |
|
In your implementation code, it is very important to never call the methods described in API for Stream Consumers above. Otherwise, you can potentially cause adverse side effects in programs that consume your streaming interfaces.
Class: stream.Readable#
stream.Readable
is an abstract class designed to be extended with an
underlying implementation of the _read(size)
method.
Please see above under API for Stream Consumers for how to consume streams in your programs. What follows is an explanation of how to implement Readable streams in your programs.
Example: A Counting Stream#
This is a basic example of a Readable stream. It emits the numerals from 1 to 1,000,000 in ascending order, and then ends.
var Readable = require('stream').Readable;
var util = require('util');
util.inherits(Counter, Readable);
function Counter(opt) {
Readable.call(this, opt);
this._max = 1000000;
this._index = 1;
}
Counter.prototype._read = function() {
var i = this._index++;
if (i > this._max)
this.push(null);
else {
var str = '' + i;
var buf = new Buffer(str, 'ascii');
this.push(buf);
}
};
Example: SimpleProtocol v1 (Sub-optimal)#
This is similar to the parseHeader
function described above, but
implemented as a custom stream. Also, note that this implementation
does not convert the incoming data to a string.
However, this would be better implemented as a Transform stream. See below for a better implementation.
// A parser for a simple data protocol.
// The "header" is a JSON object, followed by 2 \n characters, and
// then a message body.
//
// NOTE: This can be done more simply as a Transform stream!
// Using Readable directly for this is sub-optimal. See the
// alternative example below under the Transform section.
var Readable = require('stream').Readable;
var util = require('util');
util.inherits(SimpleProtocol, Readable);
function SimpleProtocol(source, options) {
if (!(this instanceof SimpleProtocol))
return new SimpleProtocol(source, options);
Readable.call(this, options);
this._inBody = false;
this._sawFirstCr = false;
// source is a readable stream, such as a socket or file
this._source = source;
var self = this;
source.on('end', function() {
self.push(null);
});
// give it a kick whenever the source is readable
// read(0) will not consume any bytes
source.on('readable', function() {
self.read(0);
});
this._rawHeader = [];
this.header = null;
}
SimpleProtocol.prototype._read = function(n) {
if (!this._inBody) {
var chunk = this._source.read();
// if the source doesn't have data, we don't have data yet.
if (chunk === null)
return this.push('');
// check if the chunk has a \n\n
var split = -1;
for (var i = 0; i < chunk.length; i++) {
if (chunk[i] === 10) { // '\n'
if (this._sawFirstCr) {
split = i;
break;
} else {
this._sawFirstCr = true;
}
} else {
this._sawFirstCr = false;
}
}
if (split === -1) {
// still waiting for the \n\n
// stash the chunk, and try again.
this._rawHeader.push(chunk);
this.push('');
} else {
this._inBody = true;
var h = chunk.slice(0, split);
this._rawHeader.push(h);
var header = Buffer.concat(this._rawHeader).toString();
try {
this.header = JSON.parse(header);
} catch (er) {
this.emit('error', new Error('invalid simple protocol data'));
return;
}
// now, because we got some extra data, unshift the rest
// back into the read queue so that our consumer will see it.
var b = chunk.slice(split);
this.unshift(b);
// and let them know that we are done parsing the header.
this.emit('header', this.header);
}
} else {
// from there on, just provide the data to our consumer.
// careful not to push(null), since that would indicate EOF.
var chunk = this._source.read();
if (chunk) this.push(chunk);
}
};
// Usage:
// var parser = new SimpleProtocol(source);
// Now parser is a readable stream that will emit 'header'
// with the parsed header data.
new stream.Readable([options])#
options
ObjecthighWaterMark
Number The maximum number of bytes to store in the internal buffer before ceasing to read from the underlying resource. Default=16kb, or 16 forobjectMode
streamsencoding
String If specified, then buffers will be decoded to strings using the specified encoding. Default=nullobjectMode
Boolean Whether this stream should behave as a stream of objects. Meaning that stream.read(n) returns a single value instead of a Buffer of size n. Default=false
In classes that extend the Readable class, make sure to call the Readable constructor so that the buffering settings can be properly initialized.
readable._read(size)#
size
Number Number of bytes to read asynchronously
Note: Implement this function, but do NOT call it directly.
This function should NOT be called directly. It should be implemented by child classes, and only called by the internal Readable class methods.
All Readable stream implementations must provide a _read
method to
fetch data from the underlying resource.
This method is prefixed with an underscore because it is internal to the class that defines it, and should not be called directly by user programs. However, you are expected to override this method in your own extension classes.
When data is available, put it into the read queue by calling
readable.push(chunk)
. If push
returns false, then you should stop
reading. When _read
is called again, you should start pushing more
data.
The size
argument is advisory. Implementations where a "read" is a
single call that returns data can use this to know how much data to
fetch. Implementations where that is not relevant, such as TCP or
TLS, may ignore this argument, and simply provide data whenever it
becomes available. There is no need, for example to "wait" until
size
bytes are available before calling stream.push(chunk)
.
readable.push(chunk, [encoding])#
chunk
Buffer | null | String Chunk of data to push into the read queueencoding
String Encoding of String chunks. Must be a valid Buffer encoding, such as'utf8'
or'ascii'
- return Boolean Whether or not more pushes should be performed
Note: This function should be called by Readable implementors, NOT by consumers of Readable streams.
The _read()
function will not be called again until at least one
push(chunk)
call is made.
The Readable
class works by putting data into a read queue to be
pulled out later by calling the read()
method when the 'readable'
event fires.
The push()
method will explicitly insert some data into the read
queue. If it is called with null
then it will signal the end of the
data (EOF).
This API is designed to be as flexible as possible. For example, you may be wrapping a lower-level source which has some sort of pause/resume mechanism, and a data callback. In those cases, you could wrap the low-level source object by doing something like this:
// source is an object with readStop() and readStart() methods,
// and an `ondata` member that gets called when it has data, and
// an `onend` member that gets called when the data is over.
util.inherits(SourceWrapper, Readable);
function SourceWrapper(options) {
Readable.call(this, options);
this._source = getLowlevelSourceObject();
var self = this;
// Every time there's data, we push it into the internal buffer.
this._source.ondata = function(chunk) {
// if push() returns false, then we need to stop reading from source
if (!self.push(chunk))
self._source.readStop();
};
// When the source ends, we push the EOF-signaling `null` chunk
this._source.onend = function() {
self.push(null);
};
}
// _read will be called when the stream wants to pull more data in
// the advisory size argument is ignored in this case.
SourceWrapper.prototype._read = function(size) {
this._source.readStart();
};
Class: stream.Writable#
stream.Writable
is an abstract class designed to be extended with an
underlying implementation of the _write(chunk, encoding, callback)
method.
Please see above under API for Stream Consumers for how to consume writable streams in your programs. What follows is an explanation of how to implement Writable streams in your programs.
new stream.Writable([options])#
options
ObjecthighWaterMark
Number Buffer level whenwrite()
starts returning false. Default=16kb, or 16 forobjectMode
streamsdecodeStrings
Boolean Whether or not to decode strings into Buffers before passing them to_write()
. Default=trueobjectMode
Boolean Whether or not thewrite(anyObj)
is a valid operation. If set you can write arbitrary data instead of onlyBuffer
/String
data. Default=false
In classes that extend the Writable class, make sure to call the constructor so that the buffering settings can be properly initialized.
writable._write(chunk, encoding, callback)#
chunk
Buffer | String The chunk to be written. Will always be a buffer unless thedecodeStrings
option was set tofalse
.encoding
String If the chunk is a string, then this is the encoding type. Ignore if chunk is a buffer. Note that chunk will always be a buffer unless thedecodeStrings
option is explicitly set tofalse
.callback
Function Call this function (optionally with an error argument) when you are done processing the supplied chunk.
All Writable stream implementations must provide a _write()
method to send data to the underlying resource.
Note: This function MUST NOT be called directly. It should be implemented by child classes, and called by the internal Writable class methods only.
Call the callback using the standard callback(error)
pattern to
signal that the write completed successfully or with an error.
If the decodeStrings
flag is set in the constructor options, then
chunk
may be a string rather than a Buffer, and encoding
will
indicate the sort of string that it is. This is to support
implementations that have an optimized handling for certain string
data encodings. If you do not explicitly set the decodeStrings
option to false
, then you can safely ignore the encoding
argument,
and assume that chunk
will always be a Buffer.
This method is prefixed with an underscore because it is internal to the class that defines it, and should not be called directly by user programs. However, you are expected to override this method in your own extension classes.
writable._writev(chunks, callback)#
chunks
Array The chunks to be written. Each chunk has following format:{ chunk: ..., encoding: ... }
.callback
Function Call this function (optionally with an error argument) when you are done processing the supplied chunks.
Note: This function MUST NOT be called directly. It may be implemented by child classes, and called by the internal Writable class methods only.
This function is completely optional to implement. In most cases it is unnecessary. If implemented, it will be called with all the chunks that are buffered in the write queue.
Class: stream.Duplex#
A "duplex" stream is one that is both Readable and Writable, such as a TCP socket connection.
Note that stream.Duplex
is an abstract class designed to be extended
with an underlying implementation of the _read(size)
and
_write(chunk, encoding, callback)
methods as you would with a
Readable or Writable stream class.
Since JavaScript doesn't have multiple prototypal inheritance, this
class prototypally inherits from Readable, and then parasitically from
Writable. It is thus up to the user to implement both the lowlevel
_read(n)
method as well as the lowlevel
_write(chunk, encoding, callback)
method on extension duplex classes.
new stream.Duplex(options)#
options
Object Passed to both Writable and Readable constructors. Also has the following fields:allowHalfOpen
Boolean Default=true. If set tofalse
, then the stream will automatically end the readable side when the writable side ends and vice versa.readableObjectMode
Boolean Default=false. SetsobjectMode
for readable side of the stream. Has no effect ifobjectMode
istrue
.writableObjectMode
Boolean Default=false. SetsobjectMode
for writable side of the stream. Has no effect ifobjectMode
istrue
.
In classes that extend the Duplex class, make sure to call the constructor so that the buffering settings can be properly initialized.
Class: stream.Transform#
A "transform" stream is a duplex stream where the output is causally connected in some way to the input, such as a zlib stream or a crypto stream.
There is no requirement that the output be the same size as the input, the same number of chunks, or arrive at the same time. For example, a Hash stream will only ever have a single chunk of output which is provided when the input is ended. A zlib stream will produce output that is either much smaller or much larger than its input.
Rather than implement the _read()
and _write()
methods, Transform
classes must implement the _transform()
method, and may optionally
also implement the _flush()
method. (See below.)
new stream.Transform([options])#
options
Object Passed to both Writable and Readable constructors.
In classes that extend the Transform class, make sure to call the constructor so that the buffering settings can be properly initialized.
transform._transform(chunk, encoding, callback)#
chunk
Buffer | String The chunk to be transformed. Will always be a buffer unless thedecodeStrings
option was set tofalse
.encoding
String If the chunk is a string, then this is the encoding type. (Ignore ifdecodeStrings
chunk is a buffer.)callback
Function Call this function (optionally with an error argument) when you are done processing the supplied chunk.
Note: This function MUST NOT be called directly. It should be implemented by child classes, and called by the internal Transform class methods only.
All Transform stream implementations must provide a _transform
method to accept input and produce output.
_transform
should do whatever has to be done in this specific
Transform class, to handle the bytes being written, and pass them off
to the readable portion of the interface. Do asynchronous I/O,
process things, and so on.
Call transform.push(outputChunk)
0 or more times to generate output
from this input chunk, depending on how much data you want to output
as a result of this chunk.
Call the callback function only when the current chunk is completely consumed. Note that there may or may not be output as a result of any particular input chunk.
This method is prefixed with an underscore because it is internal to the class that defines it, and should not be called directly by user programs. However, you are expected to override this method in your own extension classes.
transform._flush(callback)#
callback
Function Call this function (optionally with an error argument) when you are done flushing any remaining data.
Note: This function MUST NOT be called directly. It MAY be implemented by child classes, and if so, will be called by the internal Transform class methods only.
In some cases, your transform operation may need to emit a bit more
data at the end of the stream. For example, a Zlib
compression
stream will store up some internal state so that it can optimally
compress the output. At the end, however, it needs to do the best it
can with what is left, so that the data will be complete.
In those cases, you can implement a _flush
method, which will be
called at the very end, after all the written data is consumed, but
before emitting end
to signal the end of the readable side. Just
like with _transform
, call transform.push(chunk)
zero or more
times, as appropriate, and call callback
when the flush operation is
complete.
This method is prefixed with an underscore because it is internal to the class that defines it, and should not be called directly by user programs. However, you are expected to override this method in your own extension classes.
Events: 'finish' and 'end'#
The finish
and end
events are from the parent Writable
and Readable classes respectively. The finish
event is fired after
.end()
is called and all chunks have been processed by _transform
,
end
is fired after all data has been output which is after the callback
in _flush
has been called.
Example: SimpleProtocol
parser v2#
The example above of a simple protocol parser can be implemented
simply by using the higher level Transform stream class, similar to
the parseHeader
and SimpleProtocol v1
examples above.
In this example, rather than providing the input as an argument, it would be piped into the parser, which is a more idiomatic Node stream approach.
var util = require('util');
var Transform = require('stream').Transform;
util.inherits(SimpleProtocol, Transform);
function SimpleProtocol(options) {
if (!(this instanceof SimpleProtocol))
return new SimpleProtocol(options);
Transform.call(this, options);
this._inBody = false;
this._sawFirstCr = false;
this._rawHeader = [];
this.header = null;
}
SimpleProtocol.prototype._transform = function(chunk, encoding, done) {
if (!this._inBody) {
// check if the chunk has a \n\n
var split = -1;
for (var i = 0; i < chunk.length; i++) {
if (chunk[i] === 10) { // '\n'
if (this._sawFirstCr) {
split = i;
break;
} else {
this._sawFirstCr = true;
}
} else {
this._sawFirstCr = false;
}
}
if (split === -1) {
// still waiting for the \n\n
// stash the chunk, and try again.
this._rawHeader.push(chunk);
} else {
this._inBody = true;
var h = chunk.slice(0, split);
this._rawHeader.push(h);
var header = Buffer.concat(this._rawHeader).toString();
try {
this.header = JSON.parse(header);
} catch (er) {
this.emit('error', new Error('invalid simple protocol data'));
return;
}
// and let them know that we are done parsing the header.
this.emit('header', this.header);
// now, because we got some extra data, emit this first.
this.push(chunk.slice(split));
}
} else {
// from there on, just provide the data to our consumer as-is.
this.push(chunk);
}
done();
};
// Usage:
// var parser = new SimpleProtocol();
// source.pipe(parser)
// Now parser is a readable stream that will emit 'header'
// with the parsed header data.
Class: stream.PassThrough#
This is a trivial implementation of a Transform stream that simply passes the input bytes across to the output. Its purpose is mainly for examples and testing, but there are occasionally use cases where it can come in handy as a building block for novel sorts of streams.
Streams: Under the Hood#
Buffering#
Both Writable and Readable streams will buffer data on an internal
object called _writableState.buffer
or _readableState.buffer
,
respectively.
The amount of data that will potentially be buffered depends on the
highWaterMark
option which is passed into the constructor.
Buffering in Readable streams happens when the implementation calls
stream.push(chunk)
. If the consumer of the Stream does not call
stream.read()
, then the data will sit in the internal queue until it
is consumed.
Buffering in Writable streams happens when the user calls
stream.write(chunk)
repeatedly, even when write()
returns false
.
The purpose of streams, especially with the pipe()
method, is to
limit the buffering of data to acceptable levels, so that sources and
destinations of varying speed will not overwhelm the available memory.
stream.read(0)
#
There are some cases where you want to trigger a refresh of the
underlying readable stream mechanisms, without actually consuming any
data. In that case, you can call stream.read(0)
, which will always
return null.
If the internal read buffer is below the highWaterMark
, and the
stream is not currently reading, then calling read(0)
will trigger
a low-level _read
call.
There is almost never a need to do this. However, you will see some cases in Node's internals where this is done, particularly in the Readable stream class internals.
stream.push('')
#
Pushing a zero-byte string or Buffer (when not in Object mode) has an
interesting side effect. Because it is a call to
stream.push()
, it will end the reading
process. However, it
does not add any data to the readable buffer, so there's nothing for
a user to consume.
Very rarely, there are cases where you have no data to provide now,
but the consumer of your stream (or, perhaps, another bit of your own
code) will know when to check again, by calling stream.read(0)
. In
those cases, you may call stream.push('')
.
So far, the only use case for this functionality is in the
tls.CryptoStream class, which is deprecated in Node v0.12. If you
find that you have to use stream.push('')
, please consider another
approach, because it almost certainly indicates that something is
horribly wrong.
Compatibility with Older Node Versions#
In versions of Node prior to v0.10, the Readable stream interface was simpler, but also less powerful and less useful.
- Rather than waiting for you to call the
read()
method,'data'
events would start emitting immediately. If you needed to do some I/O to decide how to handle data, then you had to store the chunks in some kind of buffer so that they would not be lost. - The
pause()
method was advisory, rather than guaranteed. This meant that you still had to be prepared to receive'data'
events even when the stream was in a paused state.
In Node v0.10, the Readable class described below was added. For
backwards compatibility with older Node programs, Readable streams
switch into "flowing mode" when a 'data'
event handler is added, or
when the resume()
method is called. The effect is that, even if
you are not using the new read()
method and 'readable'
event, you
no longer have to worry about losing 'data'
chunks.
Most programs will continue to function normally. However, this introduces an edge case in the following conditions:
- No
'data'
event handler is added. - The
resume()
method is never called. - The stream is not piped to any writable destination.
For example, consider the following code:
// WARNING! BROKEN!
net.createServer(function(socket) {
// we add an 'end' method, but never consume the data
socket.on('end', function() {
// It will never get here.
socket.end('I got your message (but didnt read it)\n');
});
}).listen(1337);
In versions of node prior to v0.10, the incoming message data would be simply discarded. However, in Node v0.10 and beyond, the socket will remain paused forever.
The workaround in this situation is to call the resume()
method to
start the flow of data:
// Workaround
net.createServer(function(socket) {
socket.on('end', function() {
socket.end('I got your message (but didnt read it)\n');
});
// start the flow of data, discarding it.
socket.resume();
}).listen(1337);
In addition to new Readable streams switching into flowing mode,
pre-v0.10 style streams can be wrapped in a Readable class using the
wrap()
method.
Object Mode#
Normally, Streams operate on Strings and Buffers exclusively.
Streams that are in object mode can emit generic JavaScript values other than Buffers and Strings.
A Readable stream in object mode will always return a single item from
a call to stream.read(size)
, regardless of what the size argument
is.
A Writable stream in object mode will always ignore the encoding
argument to stream.write(data, encoding)
.
The special value null
still retains its special value for object
mode streams. That is, for object mode readable streams, null
as a
return value from stream.read()
indicates that there is no more
data, and stream.push(null)
will signal the end of stream data
(EOF
).
No streams in Node core are object mode streams. This pattern is only used by userland streaming libraries.
You should set objectMode
in your stream child class constructor on
the options object. Setting objectMode
mid-stream is not safe.
For Duplex streams objectMode
can be set exclusively for readable or
writable side with readableObjectMode
and writableObjectMode
respectively. These options can be used to implement parsers and
serializers with Transform streams.
var util = require('util');
var StringDecoder = require('string_decoder').StringDecoder;
var Transform = require('stream').Transform;
util.inherits(JSONParseStream, Transform);
// Gets \n-delimited JSON string data, and emits the parsed objects
function JSONParseStream() {
if (!(this instanceof JSONParseStream))
return new JSONParseStream();
Transform.call(this, { readableObjectMode : true });
this._buffer = '';
this._decoder = new StringDecoder('utf8');
}
JSONParseStream.prototype._transform = function(chunk, encoding, cb) {
this._buffer += this._decoder.write(chunk);
// split on newlines
var lines = this._buffer.split(/\r?\n/);
// keep the last partial line buffered
this._buffer = lines.pop();
for (var l = 0; l < lines.length; l++) {
var line = lines[l];
try {
var obj = JSON.parse(line);
} catch (er) {
this.emit('error', er);
return;
}
// push the parsed object out to the readable consumer
this.push(obj);
}
cb();
};
JSONParseStream.prototype._flush = function(cb) {
// Just handle any leftover
var rem = this._buffer.trim();
if (rem) {
try {
var obj = JSON.parse(rem);
} catch (er) {
this.emit('error', er);
return;
}
// push the parsed object out to the readable consumer
this.push(obj);
}
cb();
};
Crypto#
Stability: 2 - Unstable; API changes are being discussed for future versions. Breaking changes will be minimized. See below.
Use require('crypto')
to access this module.
The crypto module offers a way of encapsulating secure credentials to be used as part of a secure HTTPS net or http connection.
It also offers a set of wrappers for OpenSSL's hash, hmac, cipher, decipher, sign and verify methods.
crypto.setEngine(engine, [flags])#
Load and set engine for some/all OpenSSL functions (selected by flags).
engine
could be either an id or a path to the to the engine's shared library.
flags
is optional and has ENGINE_METHOD_ALL
value by default. It could take
one of or mix of following flags (defined in constants
module):
ENGINE_METHOD_RSA
ENGINE_METHOD_DSA
ENGINE_METHOD_DH
ENGINE_METHOD_RAND
ENGINE_METHOD_ECDH
ENGINE_METHOD_ECDSA
ENGINE_METHOD_CIPHERS
ENGINE_METHOD_DIGESTS
ENGINE_METHOD_STORE
ENGINE_METHOD_PKEY_METH
ENGINE_METHOD_PKEY_ASN1_METH
ENGINE_METHOD_ALL
ENGINE_METHOD_NONE
crypto.getCiphers()#
Returns an array with the names of the supported ciphers.
Example:
var ciphers = crypto.getCiphers();
console.log(ciphers); // ['AES-128-CBC', 'AES-128-CBC-HMAC-SHA1', ...]
crypto.getHashes()#
Returns an array with the names of the supported hash algorithms.
Example:
var hashes = crypto.getHashes();
console.log(hashes); // ['sha', 'sha1', 'sha1WithRSAEncryption', ...]
crypto.createCredentials(details)#
Stability: 0 - Deprecated. Use tls.createSecureContext instead.
Creates a credentials object, with the optional details being a dictionary with keys:
pfx
: A string or buffer holding the PFX or PKCS12 encoded private key, certificate and CA certificateskey
: A string holding the PEM encoded private keypassphrase
: A string of passphrase for the private key or pfxcert
: A string holding the PEM encoded certificateca
: Either a string or list of strings of PEM encoded CA certificates to trust.crl
: Either a string or list of strings of PEM encoded CRLs (Certificate Revocation List)ciphers
: A string describing the ciphers to use or exclude. Consult http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT for details on the format.
If no 'ca' details are given, then node.js will use the default publicly trusted list of CAs as given in
http://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt.
crypto.createHash(algorithm)#
Creates and returns a hash object, a cryptographic hash with the given algorithm which can be used to generate hash digests.
algorithm
is dependent on the available algorithms supported by the
version of OpenSSL on the platform. Examples are 'sha1'
, 'md5'
,
'sha256'
, 'sha512'
, etc. On recent releases, openssl
list-message-digest-algorithms
will display the available digest
algorithms.
Example: this program that takes the sha1 sum of a file
var filename = process.argv[2];
var crypto = require('crypto');
var fs = require('fs');
var shasum = crypto.createHash('sha1');
var s = fs.ReadStream(filename);
s.on('data', function(d) {
shasum.update(d);
});
s.on('end', function() {
var d = shasum.digest('hex');
console.log(d + ' ' + filename);
});
Class: Hash#
The class for creating hash digests of data.
It is a stream that is both readable and writable. The
written data is used to compute the hash. Once the writable side of
the stream is ended, use the read()
method to get the computed hash
digest. The legacy update
and digest
methods are also supported.
Returned by crypto.createHash
.
hash.update(data, [input_encoding])#
Updates the hash content with the given data
, the encoding of which
is given in input_encoding
and can be 'utf8'
, 'ascii'
or
'binary'
. If no encoding is provided and the input is a string an
encoding of 'binary'
is enforced. If data
is a Buffer
then
input_encoding
is ignored.
This can be called many times with new data as it is streamed.
hash.digest([encoding])#
Calculates the digest of all of the passed data to be hashed. The
encoding
can be 'hex'
, 'binary'
or 'base64'
. If no encoding
is provided, then a buffer is returned.
Note: hash
object can not be used after digest()
method has been
called.
crypto.createHmac(algorithm, key)#
Creates and returns a hmac object, a cryptographic hmac with the given algorithm and key.
It is a stream that is both readable and writable. The
written data is used to compute the hmac. Once the writable side of
the stream is ended, use the read()
method to get the computed
digest. The legacy update
and digest
methods are also supported.
algorithm
is dependent on the available algorithms supported by
OpenSSL - see createHash above. key
is the hmac key to be used.
Class: Hmac#
Class for creating cryptographic hmac content.
Returned by crypto.createHmac
.
hmac.update(data)#
Update the hmac content with the given data
. This can be called
many times with new data as it is streamed.
hmac.digest([encoding])#
Calculates the digest of all of the passed data to the hmac. The
encoding
can be 'hex'
, 'binary'
or 'base64'
. If no encoding
is provided, then a buffer is returned.
Note: hmac
object can not be used after digest()
method has been
called.
crypto.createCipher(algorithm, password)#
Creates and returns a cipher object, with the given algorithm and password.
algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On
recent releases, openssl list-cipher-algorithms
will display the
available cipher algorithms. password
is used to derive key and IV,
which must be a 'binary'
encoded string or a buffer.
It is a stream that is both readable and writable. The
written data is used to compute the hash. Once the writable side of
the stream is ended, use the read()
method to get the enciphered
contents. The legacy update
and final
methods are also supported.
crypto.createCipheriv(algorithm, key, iv)#
Creates and returns a cipher object, with the given algorithm, key and iv.
algorithm
is the same as the argument to createCipher()
. key
is
the raw key used by the algorithm. iv
is an initialization
vector.
key
and iv
must be 'binary'
encoded strings or
buffers.
Class: Cipher#
Class for encrypting data.
Returned by crypto.createCipher
and crypto.createCipheriv
.
Cipher objects are streams that are both readable and
writable. The written plain text data is used to produce the
encrypted data on the readable side. The legacy update
and final
methods are also supported.
cipher.update(data, [input_encoding], [output_encoding])#
Updates the cipher with data
, the encoding of which is given in
input_encoding
and can be 'utf8'
, 'ascii'
or 'binary'
. If no
encoding is provided, then a buffer is expected.
If data
is a Buffer
then input_encoding
is ignored.
The output_encoding
specifies the output format of the enciphered
data, and can be 'binary'
, 'base64'
or 'hex'
. If no encoding is
provided, then a buffer is returned.
Returns the enciphered contents, and can be called many times with new data as it is streamed.
cipher.final([output_encoding])#
Returns any remaining enciphered contents, with output_encoding
being one of: 'binary'
, 'base64'
or 'hex'
. If no encoding is
provided, then a buffer is returned.
Note: cipher
object can not be used after final()
method has been
called.
cipher.setAutoPadding(auto_padding=true)#
You can disable automatic padding of the input data to block size. If
auto_padding
is false, the length of the entire input data must be a
multiple of the cipher's block size or final
will fail. Useful for
non-standard padding, e.g. using 0x0
instead of PKCS padding. You
must call this before cipher.final
.
cipher.getAuthTag()#
For authenticated encryption modes (currently supported: GCM), this
method returns a Buffer
that represents the authentication tag that
has been computed from the given data. Should be called after
encryption has been completed using the final
method!
cipher.setAAD(buffer)#
For authenticated encryption modes (currently supported: GCM), this method sets the value used for the additional authenticated data (AAD) input parameter.
crypto.createDecipher(algorithm, password)#
Creates and returns a decipher object, with the given algorithm and key. This is the mirror of the createCipher() above.
crypto.createDecipheriv(algorithm, key, iv)#
Creates and returns a decipher object, with the given algorithm, key and iv. This is the mirror of the createCipheriv() above.
Class: Decipher#
Class for decrypting data.
Returned by crypto.createDecipher
and crypto.createDecipheriv
.
Decipher objects are streams that are both readable and
writable. The written enciphered data is used to produce the
plain-text data on the the readable side. The legacy update
and
final
methods are also supported.
decipher.update(data, [input_encoding], [output_encoding])#
Updates the decipher with data
, which is encoded in 'binary'
,
'base64'
or 'hex'
. If no encoding is provided, then a buffer is
expected.
If data
is a Buffer
then input_encoding
is ignored.
The output_decoding
specifies in what format to return the
deciphered plaintext: 'binary'
, 'ascii'
or 'utf8'
. If no
encoding is provided, then a buffer is returned.
decipher.final([output_encoding])#
Returns any remaining plaintext which is deciphered, with
output_encoding
being one of: 'binary'
, 'ascii'
or 'utf8'
. If
no encoding is provided, then a buffer is returned.
Note: decipher
object can not be used after final()
method has been
called.
decipher.setAutoPadding(auto_padding=true)#
You can disable auto padding if the data has been encrypted without
standard block padding to prevent decipher.final
from checking and
removing it. Can only work if the input data's length is a multiple of
the ciphers block size. You must call this before streaming data to
decipher.update
.
decipher.setAuthTag(buffer)#
For authenticated encryption modes (currently supported: GCM), this
method must be used to pass in the received authentication tag.
If no tag is provided or if the ciphertext has been tampered with,
final
will throw, thus indicating that the ciphertext should
be discarded due to failed authentication.
decipher.setAAD(buffer)#
For authenticated encryption modes (currently supported: GCM), this method sets the value used for the additional authenticated data (AAD) input parameter.
crypto.createSign(algorithm)#
Creates and returns a signing object, with the given algorithm. On
recent OpenSSL releases, openssl list-public-key-algorithms
will
display the available signing algorithms. Examples are 'RSA-SHA256'
.
Class: Sign#
Class for generating signatures.
Returned by crypto.createSign
.
Sign objects are writable streams. The written data is
used to generate the signature. Once all of the data has been
written, the sign
method will return the signature. The legacy
update
method is also supported.
sign.update(data)#
Updates the sign object with data. This can be called many times with new data as it is streamed.
sign.sign(private_key, [output_format])#
Calculates the signature on all the updated data passed through the sign.
private_key
can be an object or a string. If private_key
is a string, it is
treated as the key with no passphrase.
private_key
:
key
: A string holding the PEM encoded private keypassphrase
: A string of passphrase for the private key
Returns the signature in output_format
which can be 'binary'
,
'hex'
or 'base64'
. If no encoding is provided, then a buffer is
returned.
Note: sign
object can not be used after sign()
method has been
called.
crypto.createVerify(algorithm)#
Creates and returns a verification object, with the given algorithm. This is the mirror of the signing object above.
Class: Verify#
Class for verifying signatures.
Returned by crypto.createVerify
.
Verify objects are writable streams. The written data
is used to validate against the supplied signature. Once all of the
data has been written, the verify
method will return true if the
supplied signature is valid. The legacy update
method is also
supported.
verifier.update(data)#
Updates the verifier object with data. This can be called many times with new data as it is streamed.
verifier.verify(object, signature, [signature_format])#
Verifies the signed data by using the object
and signature
.
object
is a string containing a PEM encoded object, which can be
one of RSA public key, DSA public key, or X.509 certificate.
signature
is the previously calculated signature for the data, in
the signature_format
which can be 'binary'
, 'hex'
or 'base64'
.
If no encoding is specified, then a buffer is expected.
Returns true or false depending on the validity of the signature for the data and public key.
Note: verifier
object can not be used after verify()
method has been
called.
crypto.createDiffieHellman(prime_length, [generator])#
Creates a Diffie-Hellman key exchange object and generates a prime of
prime_length
bits and using an optional specific numeric generator
.
If no generator
is specified, then 2
is used.
crypto.createDiffieHellman(prime, [prime_encoding], [generator], [generator_encoding])#
Creates a Diffie-Hellman key exchange object using the supplied prime
and an
optional specific generator
.
generator
can be a number, string, or Buffer.
If no generator
is specified, then 2
is used.
prime_encoding
and generator_encoding
can be 'binary'
, 'hex'
, or 'base64'
.
If no prime_encoding
is specified, then a Buffer is expected for prime
.
If no generator_encoding
is specified, then a Buffer is expected for generator
.
Class: DiffieHellman#
The class for creating Diffie-Hellman key exchanges.
Returned by crypto.createDiffieHellman
.
diffieHellman.verifyError#
A bit field containing any warnings and/or errors as a result of a check performed
during initialization. The following values are valid for this property
(defined in constants
module):
DH_CHECK_P_NOT_SAFE_PRIME
DH_CHECK_P_NOT_PRIME
DH_UNABLE_TO_CHECK_GENERATOR
DH_NOT_SUITABLE_GENERATOR
diffieHellman.generateKeys([encoding])#
Generates private and public Diffie-Hellman key values, and returns
the public key in the specified encoding. This key should be
transferred to the other party. Encoding can be 'binary'
, 'hex'
,
or 'base64'
. If no encoding is provided, then a buffer is returned.
diffieHellman.computeSecret(other_public_key, [input_encoding], [output_encoding])#
Computes the shared secret using other_public_key
as the other
party's public key and returns the computed shared secret. Supplied
key is interpreted using specified input_encoding
, and secret is
encoded using specified output_encoding
. Encodings can be
'binary'
, 'hex'
, or 'base64'
. If the input encoding is not
provided, then a buffer is expected.
If no output encoding is given, then a buffer is returned.
diffieHellman.getPrime([encoding])#
Returns the Diffie-Hellman prime in the specified encoding, which can
be 'binary'
, 'hex'
, or 'base64'
. If no encoding is provided,
then a buffer is returned.
diffieHellman.getGenerator([encoding])#
Returns the Diffie-Hellman generator in the specified encoding, which can
be 'binary'
, 'hex'
, or 'base64'
. If no encoding is provided,
then a buffer is returned.
diffieHellman.getPublicKey([encoding])#
Returns the Diffie-Hellman public key in the specified encoding, which
can be 'binary'
, 'hex'
, or 'base64'
. If no encoding is provided,
then a buffer is returned.
diffieHellman.getPrivateKey([encoding])#
Returns the Diffie-Hellman private key in the specified encoding,
which can be 'binary'
, 'hex'
, or 'base64'
. If no encoding is
provided, then a buffer is returned.
diffieHellman.setPublicKey(public_key, [encoding])#
Sets the Diffie-Hellman public key. Key encoding can be 'binary'
,
'hex'
or 'base64'
. If no encoding is provided, then a buffer is
expected.
diffieHellman.setPrivateKey(private_key, [encoding])#
Sets the Diffie-Hellman private key. Key encoding can be 'binary'
,
'hex'
or 'base64'
. If no encoding is provided, then a buffer is
expected.
crypto.getDiffieHellman(group_name)#
Creates a predefined Diffie-Hellman key exchange object. The
supported groups are: 'modp1'
, 'modp2'
, 'modp5'
(defined in RFC
2412) and 'modp14'
, 'modp15'
, 'modp16'
, 'modp17'
,
'modp18'
(defined in RFC 3526). The returned object mimics the
interface of objects created by crypto.createDiffieHellman()
above, but will not allow to change the keys (with
diffieHellman.setPublicKey() for example). The advantage of using
this routine is that the parties don't have to generate nor exchange
group modulus beforehand, saving both processor and communication
time.
Example (obtaining a shared secret):
var crypto = require('crypto');
var alice = crypto.getDiffieHellman('modp5');
var bob = crypto.getDiffieHellman('modp5');
alice.generateKeys();
bob.generateKeys();
var alice_secret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
var bob_secret = bob.computeSecret(alice.getPublicKey(), null, 'hex');
/* alice_secret and bob_secret should be the same */
console.log(alice_secret == bob_secret);
crypto.createECDH(curve_name)#
Creates a Elliptic Curve (EC) Diffie-Hellman key exchange object using a
predefined curve specified by curve_name
string.
Class: ECDH#
The class for creating EC Diffie-Hellman key exchanges.
Returned by crypto.createECDH
.
ECDH.generateKeys([encoding[, format]])#
Generates private and public EC Diffie-Hellman key values, and returns the public key in the specified format and encoding. This key should be transferred to the other party.
Format specifies point encoding and can be 'compressed'
, 'uncompressed'
, or
'hybrid'
. If no format is provided - the point will be returned in
'uncompressed'
format.
Encoding can be 'binary'
, 'hex'
, or 'base64'
. If no encoding is provided,
then a buffer is returned.
ECDH.computeSecret(other_public_key, [input_encoding], [output_encoding])#
Computes the shared secret using other_public_key
as the other
party's public key and returns the computed shared secret. Supplied
key is interpreted using specified input_encoding
, and secret is
encoded using specified output_encoding
. Encodings can be
'binary'
, 'hex'
, or 'base64'
. If the input encoding is not
provided, then a buffer is expected.
If no output encoding is given, then a buffer is returned.
ECDH.getPublicKey([encoding[, format]])#
Returns the EC Diffie-Hellman public key in the specified encoding and format.
Format specifies point encoding and can be 'compressed'
, 'uncompressed'
, or
'hybrid'
. If no format is provided - the point will be returned in
'uncompressed'
format.
Encoding can be 'binary'
, 'hex'
, or 'base64'
. If no encoding is provided,
then a buffer is returned.
ECDH.getPrivateKey([encoding])#
Returns the EC Diffie-Hellman private key in the specified encoding,
which can be 'binary'
, 'hex'
, or 'base64'
. If no encoding is
provided, then a buffer is returned.
ECDH.setPublicKey(public_key, [encoding])#
Sets the EC Diffie-Hellman public key. Key encoding can be 'binary'
,
'hex'
or 'base64'
. If no encoding is provided, then a buffer is
expected.
ECDH.setPrivateKey(private_key, [encoding])#
Sets the EC Diffie-Hellman private key. Key encoding can be 'binary'
,
'hex'
or 'base64'
. If no encoding is provided, then a buffer is
expected.
Example (obtaining a shared secret):
var crypto = require('crypto');
var alice = crypto.createECDH('secp256k1');
var bob = crypto.createECDH('secp256k1');
alice.generateKeys();
bob.generateKeys();
var alice_secret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
var bob_secret = bob.computeSecret(alice.getPublicKey(), null, 'hex');
/* alice_secret and bob_secret should be the same */
console.log(alice_secret == bob_secret);
crypto.pbkdf2(password, salt, iterations, keylen, [digest], callback)#
Asynchronous PBKDF2 function. Applies the selected HMAC digest function
(default: SHA1) to derive a key of the requested length from the password,
salt and number of iterations. The callback gets two arguments:
(err, derivedKey)
.
Example:
crypto.pbkdf2('secret', 'salt', 4096, 512, 'sha256', function(err, key) {
if (err)
throw err;
console.log(key.toString('hex')); // 'c5e478d...1469e50'
});
You can get a list of supported digest functions with crypto.getHashes().
crypto.pbkdf2Sync(password, salt, iterations, keylen, [digest])#
Synchronous PBKDF2 function. Returns derivedKey or throws error.
crypto.randomBytes(size, [callback])#
Generates cryptographically strong pseudo-random data. Usage:
// async
crypto.randomBytes(256, function(ex, buf) {
if (ex) throw ex;
console.log('Have %d bytes of random data: %s', buf.length, buf);
});
// sync
try {
var buf = crypto.randomBytes(256);
console.log('Have %d bytes of random data: %s', buf.length, buf);
} catch (ex) {
// handle error
// most likely, entropy sources are drained
}
NOTE: Will throw error or invoke callback with error, if there is not enough
accumulated entropy to generate cryptographically strong data. In other words,
crypto.randomBytes
without callback will not block even if all entropy sources
are drained.
crypto.pseudoRandomBytes(size, [callback])#
Generates non-cryptographically strong pseudo-random data. The data returned will be unique if it is sufficiently long, but is not necessarily unpredictable. For this reason, the output of this function should never be used where unpredictability is important, such as in the generation of encryption keys.
Usage is otherwise identical to crypto.randomBytes
.
Class: Certificate#
The class used for working with signed public key & challenges. The most
common usage for this series of functions is when dealing with the <keygen>
element. http://www.openssl.org/docs/apps/spkac.html
Returned by crypto.Certificate
.
Certificate.verifySpkac(spkac)#
Returns true of false based on the validity of the SPKAC.
Certificate.exportChallenge(spkac)#
Exports the encoded public key from the supplied SPKAC.
Certificate.exportPublicKey(spkac)#
Exports the encoded challenge associated with the SPKAC.
crypto.publicEncrypt(public_key, buffer)#
Encrypts buffer
with public_key
. Only RSA is currently supported.
public_key
can be an object or a string. If public_key
is a string, it is
treated as the key with no passphrase and will use RSA_PKCS1_OAEP_PADDING
.
public_key
:
key
: A string holding the PEM encoded private keypadding
: An optional padding value, one of the following:constants.RSA_NO_PADDING
constants.RSA_PKCS1_PADDING
constants.RSA_PKCS1_OAEP_PADDING
NOTE: All paddings are defined in constants
module.
crypto.privateDecrypt(private_key, buffer)#
Decrypts buffer
with private_key
.
private_key
can be an object or a string. If private_key
is a string, it is
treated as the key with no passphrase and will use RSA_PKCS1_OAEP_PADDING
.
private_key
:
key
: A string holding the PEM encoded private keypassphrase
: An optional string of passphrase for the private keypadding
: An optional padding value, one of the following:constants.RSA_NO_PADDING
constants.RSA_PKCS1_PADDING
constants.RSA_PKCS1_OAEP_PADDING
NOTE: All paddings are defined in constants
module.
crypto.DEFAULT_ENCODING#
The default encoding to use for functions that can take either strings
or buffers. The default value is 'buffer'
, which makes it default
to using Buffer objects. This is here to make the crypto module more
easily compatible with legacy programs that expected 'binary'
to be
the default encoding.
Note that new programs will probably expect buffers, so only use this as a temporary measure.
Recent API Changes#
The Crypto module was added to Node before there was the concept of a unified Stream API, and before there were Buffer objects for handling binary data.
As such, the streaming classes don't have the typical methods found on other Node classes, and many methods accepted and returned Binary-encoded strings by default rather than Buffers. This was changed to use Buffers by default instead.
This is a breaking change for some use cases, but not all.
For example, if you currently use the default arguments to the Sign class, and then pass the results to the Verify class, without ever inspecting the data, then it will continue to work as before. Where you once got a binary string and then presented the binary string to the Verify object, you'll now get a Buffer, and present the Buffer to the Verify object.
However, if you were doing things with the string data that will not
work properly on Buffers (such as, concatenating them, storing in
databases, etc.), or you are passing binary strings to the crypto
functions without an encoding argument, then you will need to start
providing encoding arguments to specify which encoding you'd like to
use. To switch to the previous style of using binary strings by
default, set the crypto.DEFAULT_ENCODING
field to 'binary'. Note
that new programs will probably expect buffers, so only use this as a
temporary measure.
TLS (SSL)#
Stability: 3 - Stable
Use require('tls')
to access this module.
The tls
module uses OpenSSL to provide Transport Layer Security and/or
Secure Socket Layer: encrypted stream communication.
TLS/SSL is a public/private key infrastructure. Each client and each server must have a private key. A private key is created like this:
openssl genrsa -out ryans-key.pem 1024
All servers and some clients need to have a certificate. Certificates are public keys signed by a Certificate Authority or self-signed. The first step to getting a certificate is to create a "Certificate Signing Request" (CSR) file. This is done with:
openssl req -new -key ryans-key.pem -out ryans-csr.pem
To create a self-signed certificate with the CSR, do this:
openssl x509 -req -in ryans-csr.pem -signkey ryans-key.pem -out ryans-cert.pem
Alternatively you can send the CSR to a Certificate Authority for signing.
(TODO: docs on creating a CA, for now interested users should just look at
test/fixtures/keys/Makefile
in the Node source code)
To create .pfx or .p12, do this:
openssl pkcs12 -export -in agent5-cert.pem -inkey agent5-key.pem \
-certfile ca-cert.pem -out agent5.pfx
in
: certificateinkey
: private keycertfile
: all CA certs concatenated in one file likecat ca1-cert.pem ca2-cert.pem > ca-cert.pem
Client-initiated renegotiation attack mitigation#
The TLS protocol lets the client renegotiate certain aspects of the TLS session. Unfortunately, session renegotiation requires a disproportional amount of server-side resources, which makes it a potential vector for denial-of-service attacks.
To mitigate this, renegotiations are limited to three times every 10 minutes. An error is emitted on the tls.TLSSocket instance when the threshold is exceeded. The limits are configurable:
tls.CLIENT_RENEG_LIMIT
: renegotiation limit, default is 3.tls.CLIENT_RENEG_WINDOW
: renegotiation window in seconds, default is 10 minutes.
Don't change the defaults unless you know what you are doing.
To test your server, connect to it with openssl s_client -connect address:port
and tap R<CR>
(that's the letter R
followed by a carriage return) a few
times.
NPN and SNI#
NPN (Next Protocol Negotiation) and SNI (Server Name Indication) are TLS handshake extensions allowing you:
- NPN - to use one TLS server for multiple protocols (HTTP, SPDY)
- SNI - to use one TLS server for multiple hostnames with different SSL certificates.
Perfect Forward Secrecy#
The term "Forward Secrecy" or "Perfect Forward Secrecy" describes a feature of key-agreement (i.e. key-exchange) methods. Practically it means that even if the private key of a (your) server is compromised, communication can only be decrypted by eavesdroppers if they manage to obtain the key-pair specifically generated for each session.
This is achieved by randomly generating a key pair for key-agreement on every handshake (in contrary to the same key for all sessions). Methods implementing this technique, thus offering Perfect Forward Secrecy, are called "ephemeral".
Currently two methods are commonly used to achieve Perfect Forward Secrecy (note the character "E" appended to the traditional abbreviations):
- DHE - An ephemeral version of the Diffie Hellman key-agreement protocol.
- ECDHE - An ephemeral version of the Elliptic Curve Diffie Hellman key-agreement protocol.
Ephemeral methods may have some performance drawbacks, because key generation is expensive.
tls.getCiphers()#
Returns an array with the names of the supported SSL ciphers.
Example:
var ciphers = tls.getCiphers();
console.log(ciphers); // ['AES128-SHA', 'AES256-SHA', ...]
tls.createServer(options, [secureConnectionListener])#
Creates a new tls.Server. The connectionListener
argument is
automatically set as a listener for the secureConnection event. The
options
object has these possibilities:
pfx
: A string orBuffer
containing the private key, certificate and CA certs of the server in PFX or PKCS12 format. (Mutually exclusive with thekey
,cert
andca
options.)key
: A string orBuffer
containing the private key of the server in PEM format. (Could be an array of keys). (Required)passphrase
: A string of passphrase for the private key or pfx.cert
: A string orBuffer
containing the certificate key of the server in PEM format. (Could be an array of certs). (Required)ca
: An array of strings orBuffer
s of trusted certificates in PEM format. If this is omitted several well known "root" CAs will be used, like VeriSign. These are used to authorize connections.crl
: Either a string or list of strings of PEM encoded CRLs (Certificate Revocation List)ciphers
: A string describing the ciphers to use or exclude.To mitigate BEAST attacks it is recommended that you use this option in conjunction with the
honorCipherOrder
option described below to prioritize the non-CBC cipher.Defaults to
ECDHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA256:AES128-GCM-SHA256:RC4:HIGH:!MD5:!aNULL
. Consult the OpenSSL cipher list format documentation for details on the format.ECDHE-RSA-AES128-SHA256
,DHE-RSA-AES128-SHA256
andAES128-GCM-SHA256
are TLS v1.2 ciphers and used when node.js is linked against OpenSSL 1.0.1 or newer, such as the bundled version of OpenSSL. Note that it is still possible for a TLS v1.2 client to negotiate a weaker cipher unlesshonorCipherOrder
is enabled.RC4
is used as a fallback for clients that speak on older version of the TLS protocol.RC4
has in recent years come under suspicion and should be considered compromised for anything that is truly sensitive. It is speculated that state-level actors possess the ability to break it.NOTE: Previous revisions of this section suggested
AES256-SHA
as an acceptable cipher. Unfortunately,AES256-SHA
is a CBC cipher and therefore susceptible to BEAST attacks. Do not use it.ecdhCurve
: A string describing a named curve to use for ECDH key agreement or false to disable ECDH.Defaults to
prime256v1
. Consult RFC 4492 for more details.dhparam
: DH parameter file to use for DHE key agreement. Useopenssl dhparam
command to create it. If the file is invalid to load, it is silently discarded.handshakeTimeout
: Abort the connection if the SSL/TLS handshake does not finish in this many milliseconds. The default is 120 seconds.A
'clientError'
is emitted on thetls.Server
object whenever a handshake times out.honorCipherOrder
: When choosing a cipher, use the server's preferences instead of the client preferences.Although, this option is disabled by default, it is recommended that you use this option in conjunction with the
ciphers
option to mitigate BEAST attacks.Note: If SSLv2 is used, the server will send its list of preferences to the client, and the client chooses the cipher. Support for SSLv2 is disabled unless node.js was configured with
./configure --with-sslv2
.requestCert
: Iftrue
the server will request a certificate from clients that connect and attempt to verify that certificate. Default:false
.rejectUnauthorized
: Iftrue
the server will reject any connection which is not authorized with the list of supplied CAs. This option only has an effect ifrequestCert
istrue
. Default:false
.checkServerIdentity(servername, cert)
: Provide an override for checking server's hostname against the certificate. Should return an error if verification fails. Returnundefined
if passing.NPNProtocols
: An array orBuffer
of possible NPN protocols. (Protocols should be ordered by their priority).SNICallback(servername, cb)
: A function that will be called if client supports SNI TLS extension. Two argument will be passed to it:servername
, andcb
.SNICallback
should invokecb(null, ctx)
, wherectx
is a SecureContext instance. (You can usetls.createSecureContext(...)
to get proper SecureContext). IfSNICallback
wasn't provided - default callback with high-level API will be used (see below).sessionTimeout
: An integer specifying the seconds after which TLS session identifiers and TLS session tickets created by the server are timed out. See SSL_CTX_set_timeout for more details.ticketKeys
: A 48-byteBuffer
instance consisting of 16-byte prefix, 16-byte hmac key, 16-byte AES key. You could use it to accept tls session tickets on multiple instances of tls server.NOTE: Automatically shared between
cluster
module workers.sessionIdContext
: A string containing a opaque identifier for session resumption. IfrequestCert
istrue
, the default is MD5 hash value generated from command-line. Otherwise, the default is not provided.secureProtocol
: The SSL method to use, e.g.SSLv3_method
to force SSL version 3. The possible values depend on your installation of OpenSSL and are defined in the constant SSL_METHODS.
Here is a simple example echo server:
var tls = require('tls');
var fs = require('fs');
var options = {
key: fs.readFileSync('server-key.pem'),
cert: fs.readFileSync('server-cert.pem'),
// This is necessary only if using the client certificate authentication.
requestCert: true,
// This is necessary only if the client uses the self-signed certificate.
ca: [ fs.readFileSync('client-cert.pem') ]
};
var server = tls.createServer(options, function(socket) {
console.log('server connected',
socket.authorized ? 'authorized' : 'unauthorized');
socket.write("welcome!\n");
socket.setEncoding('utf8');
socket.pipe(socket);
});
server.listen(8000, function() {
console.log('server bound');
});
Or
var tls = require('tls');
var fs = require('fs');
var options = {
pfx: fs.readFileSync('server.pfx'),
// This is necessary only if using the client certificate authentication.
requestCert: true,
};
var server = tls.createServer(options, function(socket) {
console.log('server connected',
socket.authorized ? 'authorized' : 'unauthorized');
socket.write("welcome!\n");
socket.setEncoding('utf8');
socket.pipe(socket);
});
server.listen(8000, function() {
console.log('server bound');
});
You can test this server by connecting to it with openssl s_client
:
openssl s_client -connect 127.0.0.1:8000
tls.connect(options, [callback])#
tls.connect(port, [host], [options], [callback])#
Creates a new client connection to the given port
and host
(old API) or
options.port
and options.host
. (If host
is omitted, it defaults to
localhost
.) options
should be an object which specifies:
host
: Host the client should connect toport
: Port the client should connect tosocket
: Establish secure connection on a given socket rather than creating a new socket. If this option is specified,host
andport
are ignored.path
: Creates unix socket connection to path. If this option is specified,host
andport
are ignored.pfx
: A string orBuffer
containing the private key, certificate and CA certs of the client in PFX or PKCS12 format.key
: A string orBuffer
containing the private key of the client in PEM format. (Could be an array of keys).passphrase
: A string of passphrase for the private key or pfx.cert
: A string orBuffer
containing the certificate key of the client in PEM format. (Could be an array of certs).ca
: An array of strings orBuffer
s of trusted certificates in PEM format. If this is omitted several well known "root" CAs will be used, like VeriSign. These are used to authorize connections.rejectUnauthorized
: Iftrue
, the server certificate is verified against the list of supplied CAs. An'error'
event is emitted if verification fails;err.code
contains the OpenSSL error code. Default:true
.NPNProtocols
: An array of strings orBuffer
s containing supported NPN protocols.Buffer
s should have following format:0x05hello0x05world
, where first byte is next protocol name's length. (Passing array should usually be much simpler:['hello', 'world']
.)servername
: Servername for SNI (Server Name Indication) TLS extension.secureProtocol
: The SSL method to use, e.g.SSLv3_method
to force SSL version 3. The possible values depend on your installation of OpenSSL and are defined in the constant SSL_METHODS.session
: ABuffer
instance, containing TLS session.
The callback
parameter will be added as a listener for the
'secureConnect' event.
tls.connect()
returns a tls.TLSSocket object.
Here is an example of a client of echo server as described previously:
var tls = require('tls');
var fs = require('fs');
var options = {
// These are necessary only if using the client certificate authentication
key: fs.readFileSync('client-key.pem'),
cert: fs.readFileSync('client-cert.pem'),
// This is necessary only if the server uses the self-signed certificate
ca: [ fs.readFileSync('server-cert.pem') ]
};
var socket = tls.connect(8000, options, function() {
console.log('client connected',
socket.authorized ? 'authorized' : 'unauthorized');
process.stdin.pipe(socket);
process.stdin.resume();
});
socket.setEncoding('utf8');
socket.on('data', function(data) {
console.log(data);
});
socket.on('end', function() {
server.close();
});
Or
var tls = require('tls');
var fs = require('fs');
var options = {
pfx: fs.readFileSync('client.pfx')
};
var socket = tls.connect(8000, options, function() {
console.log('client connected',
socket.authorized ? 'authorized' : 'unauthorized');
process.stdin.pipe(socket);
process.stdin.resume();
});
socket.setEncoding('utf8');
socket.on('data', function(data) {
console.log(data);
});
socket.on('end', function() {
server.close();
});
Class: tls.TLSSocket#
Wrapper for instance of net.Socket, replaces internal socket read/write routines to perform transparent encryption/decryption of incoming/outgoing data.
new tls.TLSSocket(socket, options)#
Construct a new TLSSocket object from existing TCP socket.
socket
is an instance of net.Socket
options
is an object that might contain following properties:
secureContext
: An optional TLS context object fromtls.createSecureContext( ... )
isServer
: If true - TLS socket will be instantiated in server-modeserver
: An optional net.Server instancerequestCert
: Optional, see tls.createSecurePairrejectUnauthorized
: Optional, see tls.createSecurePairNPNProtocols
: Optional, see tls.createServerSNICallback
: Optional, see tls.createServersession
: Optional, aBuffer
instance, containing TLS sessionrequestOCSP
: Optional, iftrue
- OCSP status request extension would be added to client hello, andOCSPResponse
event will be emitted on socket before establishing secure communication
tls.createSecureContext(details)#
Stability: 0 - Deprecated. Use tls.createSecureContext instead.
Creates a credentials object, with the optional details being a dictionary with keys:
pfx
: A string or buffer holding the PFX or PKCS12 encoded private key, certificate and CA certificateskey
: A string holding the PEM encoded private keypassphrase
: A string of passphrase for the private key or pfxcert
: A string holding the PEM encoded certificateca
: Either a string or list of strings of PEM encoded CA certificates to trust.crl
: Either a string or list of strings of PEM encoded CRLs (Certificate Revocation List)ciphers
: A string describing the ciphers to use or exclude. Consult http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT for details on the format.honorCipherOrder
: When choosing a cipher, use the server's preferences instead of the client preferences. For further details seetls
module documentation.
If no 'ca' details are given, then node.js will use the default publicly trusted list of CAs as given in
http://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt.
tls.createSecurePair([context], [isServer], [requestCert], [rejectUnauthorized])#
Stability: 0 - Deprecated. Use tls.TLSSocket instead.
Creates a new secure pair object with two streams, one of which reads/writes encrypted data, and one reads/writes cleartext data. Generally the encrypted one is piped to/from an incoming encrypted data stream, and the cleartext one is used as a replacement for the initial encrypted stream.
credentials
: A secure context object from tls.createSecureContext( ... )isServer
: A boolean indicating whether this tls connection should be opened as a server or a client.requestCert
: A boolean indicating whether a server should request a certificate from a connecting client. Only applies to server connections.rejectUnauthorized
: A boolean indicating whether a server should automatically reject clients with invalid certificates. Only applies to servers withrequestCert
enabled.
tls.createSecurePair()
returns a SecurePair object with cleartext
and
encrypted
stream properties.
NOTE: cleartext
has the same APIs as tls.TLSSocket
Class: SecurePair#
Returned by tls.createSecurePair.
Event: 'secure'#
The event is emitted from the SecurePair once the pair has successfully established a secure connection.
Similarly to the checking for the server 'secureConnection' event, pair.cleartext.authorized should be checked to confirm whether the certificate used properly authorized.
Class: tls.Server#
This class is a subclass of net.Server
and has the same methods on it.
Instead of accepting just raw TCP connections, this accepts encrypted
connections using TLS or SSL.
Event: 'secureConnection'#
function (tlsSocket) {}
This event is emitted after a new connection has been successfully handshaked. The argument is a instance of tls.TLSSocket. It has all the common stream methods and events.
socket.authorized
is a boolean value which indicates if the
client has verified by one of the supplied certificate authorities for the
server. If socket.authorized
is false, then
socket.authorizationError
is set to describe how authorization
failed. Implied but worth mentioning: depending on the settings of the TLS
server, you unauthorized connections may be accepted.
socket.npnProtocol
is a string containing selected NPN protocol.
socket.servername
is a string containing servername requested with
SNI.
Event: 'clientError'#
function (exception, tlsSocket) { }
When a client connection emits an 'error' event before secure connection is established - it will be forwarded here.
tlsSocket
is the tls.TLSSocket that the error originated from.
Event: 'newSession'#
function (sessionId, sessionData, callback) { }
Emitted on creation of TLS session. May be used to store sessions in external
storage. callback
must be invoked eventually, otherwise no data will be
sent or received from secure connection.
NOTE: adding this event listener will have an effect only on connections established after addition of event listener.
Event: 'resumeSession'#
function (sessionId, callback) { }
Emitted when client wants to resume previous TLS session. Event listener may
perform lookup in external storage using given sessionId
, and invoke
callback(null, sessionData)
once finished. If session can't be resumed
(i.e. doesn't exist in storage) one may call callback(null, null)
. Calling
callback(err)
will terminate incoming connection and destroy socket.
NOTE: adding this event listener will have an effect only on connections established after addition of event listener.
Event: 'OCSPRequest'#
function (certificate, issuer, callback) { }
Emitted when the client sends a certificate status request. You could parse
server's current certificate to obtain OCSP url and certificate id, and after
obtaining OCSP response invoke callback(null, resp)
, where resp
is a
Buffer
instance. Both certificate
and issuer
are a Buffer
DER-representations of the primary and issuer's certificates. They could be used
to obtain OCSP certificate id and OCSP endpoint url.
Alternatively, callback(null, null)
could be called, meaning that there is no
OCSP response.
Calling callback(err)
will result in a socket.destroy(err)
call.
Typical flow:
- Client connects to server and sends
OCSPRequest
to it (via status info extension in ClientHello.) - Server receives request and invokes
OCSPRequest
event listener if present - Server grabs OCSP url from either
certificate
orissuer
and performs an OCSP request to the CA - Server receives
OCSPResponse
from CA and sends it back to client viacallback
argument - Client validates the response and either destroys socket or performs a handshake.
NOTE: issuer
could be null, if the certificate is self-signed or if the issuer
is not in the root certificates list. (You could provide an issuer via ca
option.)
NOTE: adding this event listener will have an effect only on connections established after addition of event listener.
NOTE: you may want to use some npm module like asn1.js to parse the certificates.
server.listen(port, [host], [callback])#
Begin accepting connections on the specified port
and host
. If the
host
is omitted, the server will accept connections directed to any
IPv4 address (INADDR_ANY
).
This function is asynchronous. The last parameter callback
will be called
when the server has been bound.
See net.Server
for more information.
server.close()#
Stops the server from accepting new connections. This function is
asynchronous, the server is finally closed when the server emits a 'close'
event.
server.address()#
Returns the bound address, the address family name and port of the server as reported by the operating system. See net.Server.address() for more information.
server.addContext(hostname, context)#
Add secure context that will be used if client request's SNI hostname is
matching passed hostname
(wildcards can be used). context
can contain
key
, cert
, ca
and/or any other properties from tls.createSecureContext
options
argument.
server.maxConnections#
Set this property to reject connections when the server's connection count gets high.
server.connections#
The number of concurrent connections on the server.
Class: CryptoStream#
Stability: 0 - Deprecated. Use tls.TLSSocket instead.
This is an encrypted stream.
cryptoStream.bytesWritten#
A proxy to the underlying socket's bytesWritten accessor, this will return the total bytes written to the socket, including the TLS overhead.
Class: tls.TLSSocket#
This is a wrapped version of net.Socket that does transparent encryption of written data and all required TLS negotiation.
This instance implements a duplex Stream interfaces. It has all the common stream methods and events.
Event: 'secureConnect'#
This event is emitted after a new connection has been successfully handshaked.
The listener will be called no matter if the server's certificate was
authorized or not. It is up to the user to test tlsSocket.authorized
to see if the server certificate was signed by one of the specified CAs.
If tlsSocket.authorized === false
then the error can be found in
tlsSocket.authorizationError
. Also if NPN was used - you can check
tlsSocket.npnProtocol
for negotiated protocol.
Event: 'OCSPResponse'#
function (response) { }
This event will be emitted if requestOCSP
option was set. response
is a
buffer object, containing server's OCSP response.
Traditionally, the response
is a signed object from the server's CA that
contains information about server's certificate revocation status.
tlsSocket.encrypted#
Static boolean value, always true
. May be used to distinguish TLS sockets
from regular ones.
tlsSocket.authorized#
A boolean that is true
if the peer certificate was signed by one of the
specified CAs, otherwise false
tlsSocket.authorizationError#
The reason why the peer's certificate has not been verified. This property
becomes available only when tlsSocket.authorized === false
.
tlsSocket.getPeerCertificate([ detailed ])#
Returns an object representing the peer's certificate. The returned object has
some properties corresponding to the field of the certificate. If detailed
argument is true
- the full chain with issuer
property will be returned,
if false
- only the top certificate without issuer
property.
Example:
{ subject:
{ C: 'UK',
ST: 'Acknack Ltd',
L: 'Rhys Jones',
O: 'node.js',
OU: 'Test TLS Certificate',
CN: 'localhost' },
issuerInfo:
{ C: 'UK',
ST: 'Acknack Ltd',
L: 'Rhys Jones',
O: 'node.js',
OU: 'Test TLS Certificate',
CN: 'localhost' },
issuer:
{ ... another certificate ... },
raw: < RAW DER buffer >,
valid_from: 'Nov 11 09:52:22 2009 GMT',
valid_to: 'Nov 6 09:52:22 2029 GMT',
fingerprint: '2A:7A:C2:DD:E5:F9:CC:53:72:35:99:7A:02:5A:71:38:52:EC:8A:DF',
serialNumber: 'B9B0D332A1AA5635' }
If the peer does not provide a certificate, it returns null
or an empty
object.
tlsSocket.getCipher()#
Returns an object representing the cipher name and the SSL/TLS protocol version of the current connection.
Example: { name: 'AES256-SHA', version: 'TLSv1/SSLv3' }
See SSL_CIPHER_get_name() and SSL_CIPHER_get_version() in http://www.openssl.org/docs/ssl/ssl.html#DEALING_WITH_CIPHERS for more information.
tlsSocket.renegotiate(options, callback)#
Initiate TLS renegotiation process. The options
may contain the following
fields: rejectUnauthorized
, requestCert
(See tls.createServer
for details). callback(err)
will be executed with null
as err
,
once the renegotiation is successfully completed.
NOTE: Can be used to request peer's certificate after the secure connection has been established.
ANOTHER NOTE: When running as the server, socket will be destroyed
with an error after handshakeTimeout
timeout.
tlsSocket.setMaxSendFragment(size)#
Set maximum TLS fragment size (default and maximum value is: 16384
, minimum
is: 512
). Returns true
on success, false
otherwise.
Smaller fragment size decreases buffering latency on the client: large fragments are buffered by the TLS layer until the entire fragment is received and its integrity is verified; large fragments can span multiple roundtrips, and their processing can be delayed due to packet loss or reordering. However, smaller fragments add extra TLS framing bytes and CPU overhead, which may decrease overall server throughput.
tlsSocket.getSession()#
Return ASN.1 encoded TLS session or undefined
if none was negotiated. Could
be used to speed up handshake establishment when reconnecting to the server.
tlsSocket.getTLSTicket()#
NOTE: Works only with client TLS sockets. Useful only for debugging, for
session reuse provide session
option to tls.connect
.
Return TLS session ticket or undefined
if none was negotiated.
tlsSocket.address()#
Returns the bound address, the address family name and port of the
underlying socket as reported by the operating system. Returns an
object with three properties, e.g.
{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
tlsSocket.remoteAddress#
The string representation of the remote IP address. For example,
'74.125.127.100'
or '2001:4860:a005::68'
.
tlsSocket.remoteFamily#
The string representation of the remote IP family. 'IPv4'
or 'IPv6'
.
tlsSocket.remotePort#
The numeric representation of the remote port. For example, 443
.
tlsSocket.localAddress#
The string representation of the local IP address.
tlsSocket.localPort#
The numeric representation of the local port.
StringDecoder#
Stability: 3 - Stable
To use this module, do require('string_decoder')
. StringDecoder decodes a
buffer to a string. It is a simple interface to buffer.toString()
but provides
additional support for utf8.
var StringDecoder = require('string_decoder').StringDecoder;
var decoder = new StringDecoder('utf8');
var cent = new Buffer([0xC2, 0xA2]);
console.log(decoder.write(cent));
var euro = new Buffer([0xE2, 0x82, 0xAC]);
console.log(decoder.write(euro));
Class: StringDecoder#
Accepts a single argument, encoding
which defaults to utf8
.
decoder.write(buffer)#
Returns a decoded string.
decoder.end()#
Returns any trailing bytes that were left in the buffer.
File System#
Stability: 3 - Stable
File I/O is provided by simple wrappers around standard POSIX functions. To
use this module do require('fs')
. All the methods have asynchronous and
synchronous forms.
The asynchronous form always take a completion callback as its last argument.
The arguments passed to the completion callback depend on the method, but the
first argument is always reserved for an exception. If the operation was
completed successfully, then the first argument will be null
or undefined
.
When using the synchronous form any exceptions are immediately thrown. You can use try/catch to handle exceptions or allow them to bubble up.
Here is an example of the asynchronous version:
var fs = require('fs');
fs.unlink('/tmp/hello', function (err) {
if (err) throw err;
console.log('successfully deleted /tmp/hello');
});
Here is the synchronous version:
var fs = require('fs');
fs.unlinkSync('/tmp/hello')
console.log('successfully deleted /tmp/hello');
With the asynchronous methods there is no guaranteed ordering. So the following is prone to error:
fs.rename('/tmp/hello', '/tmp/world', function (err) {
if (err) throw err;
console.log('renamed complete');
});
fs.stat('/tmp/world', function (err, stats) {
if (err) throw err;
console.log('stats: ' + JSON.stringify(stats));
});
It could be that fs.stat
is executed before fs.rename
.
The correct way to do this is to chain the callbacks.
fs.rename('/tmp/hello', '/tmp/world', function (err) {
if (err) throw err;
fs.stat('/tmp/world', function (err, stats) {
if (err) throw err;
console.log('stats: ' + JSON.stringify(stats));
});
});
In busy processes, the programmer is strongly encouraged to use the asynchronous versions of these calls. The synchronous versions will block the entire process until they complete--halting all connections.
Relative path to filename can be used, remember however that this path will be
relative to process.cwd()
.
Most fs functions let you omit the callback argument. If you do, a default callback is used that rethrows errors. To get a trace to the original call site, set the NODE_DEBUG environment variable:
$ cat script.js
function bad() {
require('fs').readFile('/');
}
bad();
$ env NODE_DEBUG=fs node script.js
fs.js:66
throw err;
^
Error: EISDIR, read
at rethrow (fs.js:61:21)
at maybeCallback (fs.js:79:42)
at Object.fs.readFile (fs.js:153:18)
at bad (/path/to/script.js:2:17)
at Object.<anonymous> (/path/to/script.js:5:1)
<etc.>
fs.rename(oldPath, newPath, callback)#
Asynchronous rename(2). No arguments other than a possible exception are given to the completion callback.
fs.renameSync(oldPath, newPath)#
Synchronous rename(2).
fs.ftruncate(fd, len, callback)#
Asynchronous ftruncate(2). No arguments other than a possible exception are given to the completion callback.
fs.ftruncateSync(fd, len)#
Synchronous ftruncate(2).
fs.truncate(path, len, callback)#
Asynchronous truncate(2). No arguments other than a possible exception are given to the completion callback.
fs.truncateSync(path, len)#
Synchronous truncate(2).
fs.chown(path, uid, gid, callback)#
Asynchronous chown(2). No arguments other than a possible exception are given to the completion callback.
fs.chownSync(path, uid, gid)#
Synchronous chown(2).
fs.fchown(fd, uid, gid, callback)#
Asynchronous fchown(2). No arguments other than a possible exception are given to the completion callback.
fs.fchownSync(fd, uid, gid)#
Synchronous fchown(2).
fs.lchown(path, uid, gid, callback)#
Asynchronous lchown(2). No arguments other than a possible exception are given to the completion callback.
fs.lchownSync(path, uid, gid)#
Synchronous lchown(2).
fs.chmod(path, mode, callback)#
Asynchronous chmod(2). No arguments other than a possible exception are given to the completion callback.
fs.chmodSync(path, mode)#
Synchronous chmod(2).
fs.fchmod(fd, mode, callback)#
Asynchronous fchmod(2). No arguments other than a possible exception are given to the completion callback.
fs.fchmodSync(fd, mode)#
Synchronous fchmod(2).
fs.lchmod(path, mode, callback)#
Asynchronous lchmod(2). No arguments other than a possible exception are given to the completion callback.
Only available on Mac OS X.
fs.lchmodSync(path, mode)#
Synchronous lchmod(2).
fs.stat(path, callback)#
Asynchronous stat(2). The callback gets two arguments (err, stats)
where
stats
is a fs.Stats object. See the fs.Stats
section below for more information.
fs.lstat(path, callback)#
Asynchronous lstat(2). The callback gets two arguments (err, stats)
where
stats
is a fs.Stats
object. lstat()
is identical to stat()
, except that if
path
is a symbolic link, then the link itself is stat-ed, not the file that it
refers to.
fs.fstat(fd, callback)#
Asynchronous fstat(2). The callback gets two arguments (err, stats)
where
stats
is a fs.Stats
object. fstat()
is identical to stat()
, except that
the file to be stat-ed is specified by the file descriptor fd
.
fs.statSync(path)#
Synchronous stat(2). Returns an instance of fs.Stats
.
fs.lstatSync(path)#
Synchronous lstat(2). Returns an instance of fs.Stats
.
fs.fstatSync(fd)#
Synchronous fstat(2). Returns an instance of fs.Stats
.
fs.link(srcpath, dstpath, callback)#
Asynchronous link(2). No arguments other than a possible exception are given to the completion callback.
fs.linkSync(srcpath, dstpath)#
Synchronous link(2).
fs.symlink(srcpath, dstpath, [type], callback)#
Asynchronous symlink(2). No arguments other than a possible exception are given
to the completion callback.
The type
argument can be set to 'dir'
, 'file'
, or 'junction'
(default
is 'file'
) and is only available on Windows (ignored on other platforms).
Note that Windows junction points require the destination path to be absolute. When using
'junction'
, the destination
argument will automatically be normalized to absolute path.
fs.symlinkSync(srcpath, dstpath, [type])#
Synchronous symlink(2).
fs.readlink(path, callback)#
Asynchronous readlink(2). The callback gets two arguments (err,
linkString)
.
fs.readlinkSync(path)#
Synchronous readlink(2). Returns the symbolic link's string value.
fs.realpath(path, [cache], callback)#
Asynchronous realpath(2). The callback
gets two arguments (err,
resolvedPath)
. May use process.cwd
to resolve relative paths. cache
is an
object literal of mapped paths that can be used to force a specific path
resolution or avoid additional fs.stat
calls for known real paths.
Example:
var cache = {'/etc':'/private/etc'};
fs.realpath('/etc/passwd', cache, function (err, resolvedPath) {
if (err) throw err;
console.log(resolvedPath);
});
fs.realpathSync(path, [cache])#
Synchronous realpath(2). Returns the resolved path.
fs.unlink(path, callback)#
Asynchronous unlink(2). No arguments other than a possible exception are given to the completion callback.
fs.unlinkSync(path)#
Synchronous unlink(2).
fs.rmdir(path, callback)#
Asynchronous rmdir(2). No arguments other than a possible exception are given to the completion callback.
fs.rmdirSync(path)#
Synchronous rmdir(2).
fs.mkdir(path, [mode], callback)#
Asynchronous mkdir(2). No arguments other than a possible exception are given
to the completion callback. mode
defaults to 0777
.
fs.mkdirSync(path, [mode])#
Synchronous mkdir(2).
fs.readdir(path, callback)#
Asynchronous readdir(3). Reads the contents of a directory.
The callback gets two arguments (err, files)
where files
is an array of
the names of the files in the directory excluding '.'
and '..'
.
fs.readdirSync(path)#
Synchronous readdir(3). Returns an array of filenames excluding '.'
and
'..'
.
fs.close(fd, callback)#
Asynchronous close(2). No arguments other than a possible exception are given to the completion callback.
fs.closeSync(fd)#
Synchronous close(2).
fs.open(path, flags, [mode], callback)#
Asynchronous file open. See open(2). flags
can be:
'r'
- Open file for reading. An exception occurs if the file does not exist.'r+'
- Open file for reading and writing. An exception occurs if the file does not exist.'rs'
- Open file for reading in synchronous mode. Instructs the operating system to bypass the local file system cache.This is primarily useful for opening files on NFS mounts as it allows you to skip the potentially stale local cache. It has a very real impact on I/O performance so don't use this flag unless you need it.
Note that this doesn't turn
fs.open()
into a synchronous blocking call. If that's what you want then you should be usingfs.openSync()
'rs+'
- Open file for reading and writing, telling the OS to open it synchronously. See notes for'rs'
about using this with caution.'w'
- Open file for writing. The file is created (if it does not exist) or truncated (if it exists).'wx'
- Like'w'
but fails ifpath
exists.'w+'
- Open file for reading and writing. The file is created (if it does not exist) or truncated (if it exists).'wx+'
- Like'w+'
but fails ifpath
exists.'a'
- Open file for appending. The file is created if it does not exist.'ax'
- Like'a'
but fails ifpath
exists.'a+'
- Open file for reading and appending. The file is created if it does not exist.'ax+'
- Like'a+'
but fails ifpath
exists.
mode
sets the file mode (permission and sticky bits), but only if the file was
created. It defaults to 0666
, readable and writeable.
The callback gets two arguments (err, fd)
.
The exclusive flag 'x'
(O_EXCL
flag in open(2)) ensures that path
is newly
created. On POSIX systems, path
is considered to exist even if it is a symlink
to a non-existent file. The exclusive flag may or may not work with network file
systems.
On Linux, positional writes don't work when the file is opened in append mode. The kernel ignores the position argument and always appends the data to the end of the file.
fs.openSync(path, flags, [mode])#
Synchronous version of fs.open()
.
fs.utimes(path, atime, mtime, callback)#
fs.utimesSync(path, atime, mtime)#
Change file timestamps of the file referenced by the supplied path.
fs.futimes(fd, atime, mtime, callback)#
fs.futimesSync(fd, atime, mtime)#
Change the file timestamps of a file referenced by the supplied file descriptor.
fs.fsync(fd, callback)#
Asynchronous fsync(2). No arguments other than a possible exception are given to the completion callback.
fs.fsyncSync(fd)#
Synchronous fsync(2).
fs.write(fd, buffer, offset, length[, position], callback)#
Write buffer
to the file specified by fd
.
offset
and length
determine the part of the buffer to be written.
position
refers to the offset from the beginning of the file where this data
should be written. If typeof position !== 'number'
, the data will be written
at the current position. See pwrite(2).
The callback will be given three arguments (err, written, buffer)
where
written
specifies how many bytes were written from buffer
.
Note that it is unsafe to use fs.write
multiple times on the same file
without waiting for the callback. For this scenario,
fs.createWriteStream
is strongly recommended.
On Linux, positional writes don't work when the file is opened in append mode. The kernel ignores the position argument and always appends the data to the end of the file.
fs.write(fd, data[, position[, encoding]], callback)#
Write data
to the file specified by fd
. If data
is not a Buffer instance
then the value will be coerced to a string.
position
refers to the offset from the beginning of the file where this data
should be written. If typeof position !== 'number'
the data will be written at
the current position. See pwrite(2).
encoding
is the expected string encoding.
The callback will receive the arguments (err, written, string)
where written
specifies how many bytes the passed string required to be written. Note that
bytes written is not the same as string characters. See
Buffer.byteLength.
Unlike when writing buffer
, the entire string must be written. No substring
may be specified. This is because the byte offset of the resulting data may not
be the same as the string offset.
Note that it is unsafe to use fs.write
multiple times on the same file
without waiting for the callback. For this scenario,
fs.createWriteStream
is strongly recommended.
On Linux, positional writes don't work when the file is opened in append mode. The kernel ignores the position argument and always appends the data to the end of the file.
fs.writeSync(fd, buffer, offset, length[, position])#
fs.writeSync(fd, data[, position[, encoding]])#
Synchronous versions of fs.write()
. Returns the number of bytes written.
fs.read(fd, buffer, offset, length, position, callback)#
Read data from the file specified by fd
.
buffer
is the buffer that the data will be written to.
offset
is the offset in the buffer to start writing at.
length
is an integer specifying the number of bytes to read.
position
is an integer specifying where to begin reading from in the file.
If position
is null
, data will be read from the current file position.
The callback is given the three arguments, (err, bytesRead, buffer)
.
fs.readSync(fd, buffer, offset, length, position)#
Synchronous version of fs.read
. Returns the number of bytesRead
.
fs.readFile(filename, [options], callback)#
filename
Stringoptions
Objectencoding
String | Null default =null
flag
String default ='r'
callback
Function
Asynchronously reads the entire contents of a file. Example:
fs.readFile('/etc/passwd', function (err, data) {
if (err) throw err;
console.log(data);
});
The callback is passed two arguments (err, data)
, where data
is the
contents of the file.
If no encoding is specified, then the raw buffer is returned.
fs.readFileSync(filename, [options])#
Synchronous version of fs.readFile
. Returns the contents of the filename
.
If the encoding
option is specified then this function returns a
string. Otherwise it returns a buffer.
fs.writeFile(filename, data, [options], callback)#
filename
Stringdata
String | Bufferoptions
Objectencoding
String | Null default ='utf8'
mode
Number default =438
(aka0666
in Octal)flag
String default ='w'
callback
Function
Asynchronously writes data to a file, replacing the file if it already exists.
data
can be a string or a buffer.
The encoding
option is ignored if data
is a buffer. It defaults
to 'utf8'
.
Example:
fs.writeFile('message.txt', 'Hello Node', function (err) {
if (err) throw err;
console.log('It\'s saved!');
});
fs.writeFileSync(filename, data, [options])#
The synchronous version of fs.writeFile
.
fs.appendFile(filename, data, [options], callback)#
filename
Stringdata
String | Bufferoptions
Objectencoding
String | Null default ='utf8'
mode
Number default =438
(aka0666
in Octal)flag
String default ='a'
callback
Function
Asynchronously append data to a file, creating the file if it not yet exists.
data
can be a string or a buffer.
Example:
fs.appendFile('message.txt', 'data to append', function (err) {
if (err) throw err;
console.log('The "data to append" was appended to file!');
});
fs.appendFileSync(filename, data, [options])#
The synchronous version of fs.appendFile
.
fs.watchFile(filename, [options], listener)#
Stability: 2 - Unstable. Use fs.watch instead, if possible.
Watch for changes on filename
. The callback listener
will be called each
time the file is accessed.
The second argument is optional. The options
if provided should be an object
containing two members a boolean, persistent
, and interval
. persistent
indicates whether the process should continue to run as long as files are
being watched. interval
indicates how often the target should be polled,
in milliseconds. The default is { persistent: true, interval: 5007 }
.
The listener
gets two arguments the current stat object and the previous
stat object:
fs.watchFile('message.text', function (curr, prev) {
console.log('the current mtime is: ' + curr.mtime);
console.log('the previous mtime was: ' + prev.mtime);
});
These stat objects are instances of fs.Stat
.
If you want to be notified when the file was modified, not just accessed
you need to compare curr.mtime
and prev.mtime
.
fs.unwatchFile(filename, [listener])#
Stability: 2 - Unstable. Use fs.watch instead, if possible.
Stop watching for changes on filename
. If listener
is specified, only that
particular listener is removed. Otherwise, all listeners are removed and you
have effectively stopped watching filename
.
Calling fs.unwatchFile()
with a filename that is not being watched is a
no-op, not an error.
fs.watch(filename, [options], [listener])#
Stability: 2 - Unstable.
Watch for changes on filename
, where filename
is either a file or a
directory. The returned object is a fs.FSWatcher.
The second argument is optional. The options
if provided should be an object.
The supported boolean members are persistent
and recursive
. persistent
indicates whether the process should continue to run as long as files are being
watched. recursive
indicates whether all subdirectories should be watched, or
only the current directory. This applies when a directory is specified, and only
on supported platforms (See Caveats below).
The default is { persistent: true, recursive: false }
.
The listener callback gets two arguments (event, filename)
. event
is either
'rename' or 'change', and filename
is the name of the file which triggered
the event.
Caveats#
The fs.watch
API is not 100% consistent across platforms, and is
unavailable in some situations.
The recursive option is currently supported on OS X. Only FSEvents supports this type of file watching so it is unlikely any additional platforms will be added soon.
Availability#
This feature depends on the underlying operating system providing a way to be notified of filesystem changes.
- On Linux systems, this uses
inotify
. - On BSD systems, this uses
kqueue
. - On OS X, this uses
kqueue
for files and 'FSEvents' for directories. - On SunOS systems (including Solaris and SmartOS), this uses
event ports
. - On Windows systems, this feature depends on
ReadDirectoryChangesW
.
If the underlying functionality is not available for some reason, then
fs.watch
will not be able to function. For example, watching files or
directories on network file systems (NFS, SMB, etc.) often doesn't work
reliably or at all.
You can still use fs.watchFile
, which uses stat polling, but it is slower and
less reliable.
Filename Argument#
Providing filename
argument in the callback is not supported
on every platform (currently it's only supported on Linux and Windows). Even
on supported platforms filename
is not always guaranteed to be provided.
Therefore, don't assume that filename
argument is always provided in the
callback, and have some fallback logic if it is null.
fs.watch('somedir', function (event, filename) {
console.log('event is: ' + event);
if (filename) {
console.log('filename provided: ' + filename);
} else {
console.log('filename not provided');
}
});
fs.exists(path, callback)#
Test whether or not the given path exists by checking with the file system.
Then call the callback
argument with either true or false. Example:
fs.exists('/etc/passwd', function (exists) {
util.debug(exists ? "it's there" : "no passwd!");
});
fs.exists()
is an anachronism and exists only for historical reasons.
There should almost never be a reason to use it in your own code.
In particular, checking if a file exists before opening it is an anti-pattern
that leaves you vulnerable to race conditions: another process may remove the
file between the calls to fs.exists()
and fs.open()
. Just open the file
and handle the error when it's not there.
fs.existsSync(path)#
Synchronous version of fs.exists
.
Class: fs.Stats#
Objects returned from fs.stat()
, fs.lstat()
and fs.fstat()
and their
synchronous counterparts are of this type.
stats.isFile()
stats.isDirectory()
stats.isBlockDevice()
stats.isCharacterDevice()
stats.isSymbolicLink()
(only valid withfs.lstat()
)stats.isFIFO()
stats.isSocket()
For a regular file util.inspect(stats)
would return a string very
similar to this:
{ dev: 2114,
ino: 48064969,
mode: 33188,
nlink: 1,
uid: 85,
gid: 100,
rdev: 0,
size: 527,
blksize: 4096,
blocks: 8,
atime: Mon, 10 Oct 2011 23:24:11 GMT,
mtime: Mon, 10 Oct 2011 23:24:11 GMT,
ctime: Mon, 10 Oct 2011 23:24:11 GMT,
birthtime: Mon, 10 Oct 2011 23:24:11 GMT }
Please note that atime
, mtime
, birthtime
, and ctime
are
instances of Date object and to compare the values of
these objects you should use appropriate methods. For most general
uses getTime() will return the number of
milliseconds elapsed since 1 January 1970 00:00:00 UTC and this
integer should be sufficient for any comparison, however there are
additional methods which can be used for displaying fuzzy information.
More details can be found in the MDN JavaScript Reference
page.
Stat Time Values#
The times in the stat object have the following semantics:
atime
"Access Time" - Time when file data last accessed. Changed by themknod(2)
,utimes(2)
, andread(2)
system calls.mtime
"Modified Time" - Time when file data last modified. Changed by themknod(2)
,utimes(2)
, andwrite(2)
system calls.ctime
"Change Time" - Time when file status was last changed (inode data modification). Changed by thechmod(2)
,chown(2)
,link(2)
,mknod(2)
,rename(2)
,unlink(2)
,utimes(2)
,read(2)
, andwrite(2)
system calls.birthtime
"Birth Time" - Time of file creation. Set once when the file is created. On filesystems where birthtime is not available, this field may instead hold either thectime
or1970-01-01T00:00Z
(ie, unix epoch timestamp0
). On Darwin and other FreeBSD variants, also set if theatime
is explicitly set to an earlier value than the currentbirthtime
using theutimes(2)
system call.
Prior to Node v0.12, the ctime
held the birthtime
on Windows
systems. Note that as of v0.12, ctime
is not "creation time", and
on Unix systems, it never was.
fs.createReadStream(path, [options])#
Returns a new ReadStream object (See Readable Stream
).
options
is an object with the following defaults:
{ flags: 'r',
encoding: null,
fd: null,
mode: 0666,
autoClose: true
}
options
can include start
and end
values to read a range of bytes from
the file instead of the entire file. Both start
and end
are inclusive and
start at 0. The encoding
can be 'utf8'
, 'ascii'
, or 'base64'
.
If autoClose
is false, then the file descriptor won't be closed, even if
there's an error. It is your responsibility to close it and make sure
there's no file descriptor leak. If autoClose
is set to true (default
behavior), on error
or end
the file descriptor will be closed
automatically.
An example to read the last 10 bytes of a file which is 100 bytes long:
fs.createReadStream('sample.txt', {start: 90, end: 99});
Class: fs.ReadStream#
ReadStream
is a Readable Stream.
Event: 'open'#
fd
Integer file descriptor used by the ReadStream.
Emitted when the ReadStream's file is opened.
fs.createWriteStream(path, [options])#
Returns a new WriteStream object (See Writable Stream
).
options
is an object with the following defaults:
{ flags: 'w',
encoding: null,
mode: 0666 }
options
may also include a start
option to allow writing data at
some position past the beginning of the file. Modifying a file rather
than replacing it may require a flags
mode of r+
rather than the
default mode w
.
Class: fs.WriteStream#
WriteStream
is a Writable Stream.
Event: 'open'#
fd
Integer file descriptor used by the WriteStream.
Emitted when the WriteStream's file is opened.
file.bytesWritten#
The number of bytes written so far. Does not include data that is still queued for writing.
Class: fs.FSWatcher#
Objects returned from fs.watch()
are of this type.
watcher.close()#
Stop watching for changes on the given fs.FSWatcher
.
Event: 'change'#
event
String The type of fs changefilename
String The filename that changed (if relevant/available)
Emitted when something changes in a watched directory or file. See more details in fs.watch.
Event: 'error'#
error
Error object
Emitted when an error occurs.
Path#
Stability: 3 - Stable
This module contains utilities for handling and transforming file paths. Almost all these methods perform only string transformations. The file system is not consulted to check whether paths are valid.
Use require('path')
to use this module. The following methods are provided:
path.normalize(p)#
Normalize a string path, taking care of '..'
and '.'
parts.
When multiple slashes are found, they're replaced by a single one; when the path contains a trailing slash, it is preserved. On Windows backslashes are used.
Example:
path.normalize('/foo/bar//baz/asdf/quux/..')
// returns
'/foo/bar/baz/asdf'
path.join([path1], [path2], [...])#
Join all arguments together and normalize the resulting path.
Arguments must be strings. In v0.8, non-string arguments were silently ignored. In v0.10 and up, an exception is thrown.
Example:
path.join('/foo', 'bar', 'baz/asdf', 'quux', '..')
// returns
'/foo/bar/baz/asdf'
path.join('foo', {}, 'bar')
// throws exception
TypeError: Arguments to path.join must be strings
path.resolve([from ...], to)#
Resolves to
to an absolute path.
If to
isn't already absolute from
arguments are prepended in right to left
order, until an absolute path is found. If after using all from
paths still
no absolute path is found, the current working directory is used as well. The
resulting path is normalized, and trailing slashes are removed unless the path
gets resolved to the root directory. Non-string from
arguments are ignored.
Another way to think of it is as a sequence of cd
commands in a shell.
path.resolve('foo/bar', '/tmp/file/', '..', 'a/../subfile')
Is similar to:
cd foo/bar
cd /tmp/file/
cd ..
cd a/../subfile
pwd
The difference is that the different paths don't need to exist and may also be files.
Examples:
path.resolve('/foo/bar', './baz')
// returns
'/foo/bar/baz'
path.resolve('/foo/bar', '/tmp/file/')
// returns
'/tmp/file'
path.resolve('wwwroot', 'static_files/png/', '../gif/image.gif')
// if currently in /home/myself/node, it returns
'/home/myself/node/wwwroot/static_files/gif/image.gif'
path.isAbsolute(path)#
Determines whether path
is an absolute path. An absolute path will always
resolve to the same location, regardless of the working directory.
Posix examples:
path.isAbsolute('/foo/bar') // true
path.isAbsolute('/baz/..') // true
path.isAbsolute('qux/') // false
path.isAbsolute('.') // false
Windows examples:
path.isAbsolute('//server') // true
path.isAbsolute('C:/foo/..') // true
path.isAbsolute('bar\\baz') // false
path.isAbsolute('.') // false
path.relative(from, to)#
Solve the relative path from from
to to
.
At times we have two absolute paths, and we need to derive the relative
path from one to the other. This is actually the reverse transform of
path.resolve
, which means we see that:
path.resolve(from, path.relative(from, to)) == path.resolve(to)
Examples:
path.relative('C:\\orandea\\test\\aaa', 'C:\\orandea\\impl\\bbb')
// returns
'..\\..\\impl\\bbb'
path.relative('/data/orandea/test/aaa', '/data/orandea/impl/bbb')
// returns
'../../impl/bbb'
path.dirname(p)#
Return the directory name of a path. Similar to the Unix dirname
command.
Example:
path.dirname('/foo/bar/baz/asdf/quux')
// returns
'/foo/bar/baz/asdf'
path.basename(p, [ext])#
Return the last portion of a path. Similar to the Unix basename
command.
Example:
path.basename('/foo/bar/baz/asdf/quux.html')
// returns
'quux.html'
path.basename('/foo/bar/baz/asdf/quux.html', '.html')
// returns
'quux'
path.extname(p)#
Return the extension of the path, from the last '.' to end of string in the last portion of the path. If there is no '.' in the last portion of the path or the first character of it is '.', then it returns an empty string. Examples:
path.extname('index.html')
// returns
'.html'
path.extname('index.coffee.md')
// returns
'.md'
path.extname('index.')
// returns
'.'
path.extname('index')
// returns
''
path.sep#
The platform-specific file separator. '\\'
or '/'
.
An example on *nix:
'foo/bar/baz'.split(path.sep)
// returns
['foo', 'bar', 'baz']
An example on Windows:
'foo\\bar\\baz'.split(path.sep)
// returns
['foo', 'bar', 'baz']
path.delimiter#
The platform-specific path delimiter, ;
or ':'
.
An example on *nix:
console.log(process.env.PATH)
// '/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin'
process.env.PATH.split(path.delimiter)
// returns
['/usr/bin', '/bin', '/usr/sbin', '/sbin', '/usr/local/bin']
An example on Windows:
console.log(process.env.PATH)
// 'C:\Windows\system32;C:\Windows;C:\Program Files\nodejs\'
process.env.PATH.split(path.delimiter)
// returns
['C:\Windows\system32', 'C:\Windows', 'C:\Program Files\nodejs\']
net#
Stability: 3 - Stable
The net
module provides you with an asynchronous network wrapper. It contains
methods for creating both servers and clients (called streams). You can include
this module with require('net');
net.createServer([options], [connectionListener])#
Creates a new TCP server. The connectionListener
argument is
automatically set as a listener for the 'connection' event.
options
is an object with the following defaults:
{ allowHalfOpen: false
}
If allowHalfOpen
is true
, then the socket won't automatically send a FIN
packet when the other end of the socket sends a FIN packet. The socket becomes
non-readable, but still writable. You should call the end()
method explicitly.
See 'end' event for more information.
Here is an example of an echo server which listens for connections on port 8124:
var net = require('net');
var server = net.createServer(function(c) { //'connection' listener
console.log('server connected');
c.on('end', function() {
console.log('server disconnected');
});
c.write('hello\r\n');
c.pipe(c);
});
server.listen(8124, function() { //'listening' listener
console.log('server bound');
});
Test this by using telnet
:
telnet localhost 8124
To listen on the socket /tmp/echo.sock
the third line from the last would
just be changed to
server.listen('/tmp/echo.sock', function() { //'listening' listener
Use nc
to connect to a UNIX domain socket server:
nc -U /tmp/echo.sock
net.connect(options, [connectionListener])#
net.createConnection(options, [connectionListener])#
A factory method, which returns a new 'net.Socket' and connects to the supplied address and port.
When the socket is established, the 'connect' event will be emitted.
Has the same events as 'net.Socket'.
For TCP sockets, options
argument should be an object which specifies:
port
: Port the client should connect to (Required).host
: Host the client should connect to. Defaults to'localhost'
.localAddress
: Local interface to bind to for network connections.localPort
: Local port to bind to for network connections.family
: Version of IP stack. Defaults to4
.
For local domain sockets, options
argument should be an object which
specifies:
path
: Path the client should connect to (Required).
Common options are:
allowHalfOpen
: iftrue
, the socket won't automatically send a FIN packet when the other end of the socket sends a FIN packet. Defaults tofalse
. See 'end' event for more information.
The connectListener
parameter will be added as an listener for the
'connect' event.
Here is an example of a client of echo server as described previously:
var net = require('net');
var client = net.connect({port: 8124},
function() { //'connect' listener
console.log('client connected');
client.write('world!\r\n');
});
client.on('data', function(data) {
console.log(data.toString());
client.end();
});
client.on('end', function() {
console.log('client disconnected');
});
To connect on the socket /tmp/echo.sock
the second line would just be
changed to
var client = net.connect({path: '/tmp/echo.sock'});
net.connect(port, [host], [connectListener])#
net.createConnection(port, [host], [connectListener])#
Creates a TCP connection to port
on host
. If host
is omitted,
'localhost'
will be assumed.
The connectListener
parameter will be added as an listener for the
'connect' event.
Is a factory method which returns a new 'net.Socket'.
net.connect(path, [connectListener])#
net.createConnection(path, [connectListener])#
Creates unix socket connection to path
.
The connectListener
parameter will be added as an listener for the
'connect' event.
A factory method which returns a new 'net.Socket'.
Class: net.Server#
This class is used to create a TCP or local server.
server.listen(port, [host], [backlog], [callback])#
Begin accepting connections on the specified port
and host
. If the
host
is omitted, the server will accept connections directed to any
IPv4 address (INADDR_ANY
). A port value of zero will assign a random port.
Backlog is the maximum length of the queue of pending connections.
The actual length will be determined by your OS through sysctl settings such as
tcp_max_syn_backlog
and somaxconn
on linux. The default value of this
parameter is 511 (not 512).
This function is asynchronous. When the server has been bound,
'listening' event will be emitted. The last parameter callback
will be added as an listener for the 'listening' event.
One issue some users run into is getting EADDRINUSE
errors. This means that
another server is already running on the requested port. One way of handling this
would be to wait a second and then try again. This can be done with
server.on('error', function (e) {
if (e.code == 'EADDRINUSE') {
console.log('Address in use, retrying...');
setTimeout(function () {
server.close();
server.listen(PORT, HOST);
}, 1000);
}
});
(Note: All sockets in Node set SO_REUSEADDR
already)
server.listen(path, [callback])#
path
Stringcallback
Function
Start a local socket server listening for connections on the given path
.
This function is asynchronous. When the server has been bound,
'listening' event will be emitted. The last parameter callback
will be added as an listener for the 'listening' event.
On UNIX, the local domain is usually known as the UNIX domain. The path is a filesystem path name. It is subject to the same naming conventions and permissions checks as would be done on file creation, will be visible in the filesystem, and will persist until unlinked.
On Windows, the local domain is implemented using a named pipe. The path must
refer to an entry in \\?\pipe\
or \\.\pipe\
. Any characters are permitted,
but the latter may do some processing of pipe names, such as resolving ..
sequences. Despite appearances, the pipe name space is flat. Pipes will not
persist, they are removed when the last reference to them is closed. Do not
forget javascript string escaping requires paths to be specified with
double-backslashes, such as:
net.createServer().listen(
path.join('\\\\?\\pipe', process.cwd(), 'myctl'))
server.listen(handle, [callback])#
handle
Objectcallback
Function
The handle
object can be set to either a server or socket (anything
with an underlying _handle
member), or a {fd: <n>}
object.
This will cause the server to accept connections on the specified handle, but it is presumed that the file descriptor or handle has already been bound to a port or domain socket.
Listening on a file descriptor is not supported on Windows.
This function is asynchronous. When the server has been bound,
'listening' event will be emitted.
the last parameter callback
will be added as an listener for the
'listening' event.
server.listen(options, [callback])#
options
Object - Required. Supports the following properties:port
Number - Optional.host
String - Optional.backlog
Number - Optional.path
String - Optional.exclusive
Boolean - Optional.
callback
Function - Optional.
The port
, host
, and backlog
properties of options
, as well as the
optional callback function, behave as they do on a call to
server.listen(port, [host], [backlog], [callback])
. Alternatively, the path
option can be used to specify a UNIX socket.
If exclusive
is false
(default), then cluster workers will use the same
underlying handle, allowing connection handling duties to be shared. When
exclusive
is true
, the handle is not shared, and attempted port sharing
results in an error. An example which listens on an exclusive port is
shown below.
server.listen({
host: 'localhost',
port: 80,
exclusive: true
});
server.close([callback])#
Stops the server from accepting new connections and keeps existing
connections. This function is asynchronous, the server is finally
closed when all connections are ended and the server emits a 'close'
event. Optionally, you can pass a callback to listen for the 'close'
event. If present, the callback is invoked with any potential error
as the first and only argument.
server.address()#
Returns the bound address, the address family name and port of the server
as reported by the operating system.
Useful to find which port was assigned when giving getting an OS-assigned address.
Returns an object with three properties, e.g.
{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
Example:
var server = net.createServer(function (socket) {
socket.end("goodbye\n");
});
// grab a random port.
server.listen(function() {
address = server.address();
console.log("opened server on %j", address);
});
Don't call server.address()
until the 'listening'
event has been emitted.
server.unref()#
Calling unref
on a server will allow the program to exit if this is the only
active server in the event system. If the server is already unref
d calling
unref
again will have no effect.
server.ref()#
Opposite of unref
, calling ref
on a previously unref
d server will not
let the program exit if it's the only server left (the default behavior). If
the server is ref
d calling ref
again will have no effect.
server.maxConnections#
Set this property to reject connections when the server's connection count gets high.
It is not recommended to use this option once a socket has been sent to a child
with child_process.fork()
.
server.connections#
This function is deprecated; please use server.getConnections() instead. The number of concurrent connections on the server.
This becomes null
when sending a socket to a child with
child_process.fork()
. To poll forks and get current number of active
connections use asynchronous server.getConnections
instead.
server.getConnections(callback)#
Asynchronously get the number of concurrent connections on the server. Works when sockets were sent to forks.
Callback should take two arguments err
and count
.
net.Server
is an EventEmitter with the following events:
Event: 'listening'#
Emitted when the server has been bound after calling server.listen
.
Event: 'connection'#
- Socket object The connection object
Emitted when a new connection is made. socket
is an instance of
net.Socket
.
Event: 'close'#
Emitted when the server closes. Note that if connections exist, this event is not emitted until all connections are ended.
Event: 'error'#
- Error Object
Emitted when an error occurs. The 'close'
event will be called directly
following this event. See example in discussion of server.listen
.
Class: net.Socket#
This object is an abstraction of a TCP or local socket. net.Socket
instances implement a duplex Stream interface. They can be created by the
user and used as a client (with connect()
) or they can be created by Node
and passed to the user through the 'connection'
event of a server.
new net.Socket([options])#
Construct a new socket object.
options
is an object with the following defaults:
{ fd: null
allowHalfOpen: false,
readable: false,
writable: false
}
fd
allows you to specify the existing file descriptor of socket.
Set readable
and/or writable
to true
to allow reads and/or writes on this
socket (NOTE: Works only when fd
is passed).
About allowHalfOpen
, refer to createServer()
and 'end'
event.
socket.connect(port, [host], [connectListener])#
socket.connect(path, [connectListener])#
Opens the connection for a given socket. If port
and host
are given,
then the socket will be opened as a TCP socket, if host
is omitted,
localhost
will be assumed. If a path
is given, the socket will be
opened as a unix socket to that path.
Normally this method is not needed, as net.createConnection
opens the
socket. Use this only if you are implementing a custom Socket.
This function is asynchronous. When the 'connect' event is emitted the
socket is established. If there is a problem connecting, the 'connect'
event
will not be emitted, the 'error'
event will be emitted with the exception.
The connectListener
parameter will be added as an listener for the
'connect' event.
socket.bufferSize#
net.Socket
has the property that socket.write()
always works. This is to
help users get up and running quickly. The computer cannot always keep up
with the amount of data that is written to a socket - the network connection
simply might be too slow. Node will internally queue up the data written to a
socket and send it out over the wire when it is possible. (Internally it is
polling on the socket's file descriptor for being writable).
The consequence of this internal buffering is that memory may grow. This property shows the number of characters currently buffered to be written. (Number of characters is approximately equal to the number of bytes to be written, but the buffer may contain strings, and the strings are lazily encoded, so the exact number of bytes is not known.)
Users who experience large or growing bufferSize
should attempt to
"throttle" the data flows in their program with pause()
and resume()
.
socket.setEncoding([encoding])#
Set the encoding for the socket as a Readable Stream. See stream.setEncoding() for more information.
socket.write(data, [encoding], [callback])#
Sends data on the socket. The second parameter specifies the encoding in the case of a string--it defaults to UTF8 encoding.
Returns true
if the entire data was flushed successfully to the kernel
buffer. Returns false
if all or part of the data was queued in user memory.
'drain'
will be emitted when the buffer is again free.
The optional callback
parameter will be executed when the data is finally
written out - this may not be immediately.
socket.end([data], [encoding])#
Half-closes the socket. i.e., it sends a FIN packet. It is possible the server will still send some data.
If data
is specified, it is equivalent to calling
socket.write(data, encoding)
followed by socket.end()
.
socket.destroy()#
Ensures that no more I/O activity happens on this socket. Only necessary in case of errors (parse error or so).
socket.pause()#
Pauses the reading of data. That is, 'data'
events will not be emitted.
Useful to throttle back an upload.
socket.resume()#
Resumes reading after a call to pause()
.
socket.setTimeout(timeout, [callback])#
Sets the socket to timeout after timeout
milliseconds of inactivity on
the socket. By default net.Socket
do not have a timeout.
When an idle timeout is triggered the socket will receive a 'timeout'
event but the connection will not be severed. The user must manually end()
or destroy()
the socket.
If timeout
is 0, then the existing idle timeout is disabled.
The optional callback
parameter will be added as a one time listener for the
'timeout'
event.
socket.setNoDelay([noDelay])#
Disables the Nagle algorithm. By default TCP connections use the Nagle
algorithm, they buffer data before sending it off. Setting true
for
noDelay
will immediately fire off data each time socket.write()
is called.
noDelay
defaults to true
.
socket.setKeepAlive([enable], [initialDelay])#
Enable/disable keep-alive functionality, and optionally set the initial
delay before the first keepalive probe is sent on an idle socket.
enable
defaults to false
.
Set initialDelay
(in milliseconds) to set the delay between the last
data packet received and the first keepalive probe. Setting 0 for
initialDelay will leave the value unchanged from the default
(or previous) setting. Defaults to 0
.
socket.address()#
Returns the bound address, the address family name and port of the
socket as reported by the operating system. Returns an object with
three properties, e.g.
{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
socket.unref()#
Calling unref
on a socket will allow the program to exit if this is the only
active socket in the event system. If the socket is already unref
d calling
unref
again will have no effect.
socket.ref()#
Opposite of unref
, calling ref
on a previously unref
d socket will not
let the program exit if it's the only socket left (the default behavior). If
the socket is ref
d calling ref
again will have no effect.
socket.remoteAddress#
The string representation of the remote IP address. For example,
'74.125.127.100'
or '2001:4860:a005::68'
.
socket.remoteFamily#
The string representation of the remote IP family. 'IPv4'
or 'IPv6'
.
socket.remotePort#
The numeric representation of the remote port. For example,
80
or 21
.
socket.localAddress#
The string representation of the local IP address the remote client is
connecting on. For example, if you are listening on '0.0.0.0'
and the
client connects on '192.168.1.1'
, the value would be '192.168.1.1'
.
socket.localPort#
The numeric representation of the local port. For example,
80
or 21
.
socket.bytesRead#
The amount of received bytes.
socket.bytesWritten#
The amount of bytes sent.
net.Socket
instances are EventEmitter with the following events:
Event: 'lookup'#
Emitted after resolving the hostname but before connecting. Not applicable to UNIX sockets.
err
{Error | Null} The error object. See [dns.lookup()][].address
{String} The IP address.family
{String | Null} The address type. See [dns.lookup()][].
Event: 'connect'#
Emitted when a socket connection is successfully established.
See connect()
.
Event: 'data'#
- Buffer object
Emitted when data is received. The argument data
will be a Buffer
or
String
. Encoding of data is set by socket.setEncoding()
.
(See the Readable Stream section for more information.)
Note that the data will be lost if there is no listener when a Socket
emits a 'data'
event.
Event: 'end'#
Emitted when the other end of the socket sends a FIN packet.
By default (allowHalfOpen == false
) the socket will destroy its file
descriptor once it has written out its pending write queue. However, by
setting allowHalfOpen == true
the socket will not automatically end()
its side allowing the user to write arbitrary amounts of data, with the
caveat that the user is required to end()
their side now.
Event: 'timeout'#
Emitted if the socket times out from inactivity. This is only to notify that the socket has been idle. The user must manually close the connection.
See also: socket.setTimeout()
Event: 'drain'#
Emitted when the write buffer becomes empty. Can be used to throttle uploads.
See also: the return values of socket.write()
Event: 'error'#
- Error object
Emitted when an error occurs. The 'close'
event will be called directly
following this event.
Event: 'close'#
had_error
Boolean true if the socket had a transmission error
Emitted once the socket is fully closed. The argument had_error
is a boolean
which says if the socket was closed due to a transmission error.
net.isIP(input)#
Tests if input is an IP address. Returns 0 for invalid strings, returns 4 for IP version 4 addresses, and returns 6 for IP version 6 addresses.
net.isIPv4(input)#
Returns true if input is a version 4 IP address, otherwise returns false.
net.isIPv6(input)#
Returns true if input is a version 6 IP address, otherwise returns false.
UDP / Datagram Sockets#
Stability: 3 - Stable
Datagram sockets are available through require('dgram')
.
Important note: the behavior of dgram.Socket#bind()
has changed in v0.10
and is always asynchronous now. If you have code that looks like this:
var s = dgram.createSocket('udp4');
s.bind(1234);
s.addMembership('224.0.0.114');
You have to change it to this:
var s = dgram.createSocket('udp4');
s.bind(1234, function() {
s.addMembership('224.0.0.114');
});
dgram.createSocket(type, [callback])#
dgram.createSocket(options, [callback])#
type
String. Either 'udp4' or 'udp6'options
Object. Should contain atype
property and could containreuseAddr
property.false
by default. WhenreuseAddr
istrue
-socket.bind()
will reuse address, even if the other process has already bound a socket on it.callback
Function. Attached as a listener tomessage
events. Optional- Returns: Socket object
Creates a datagram Socket of the specified types. Valid types are udp4
and udp6
.
Takes an optional callback which is added as a listener for message
events.
Call socket.bind
if you want to receive datagrams. socket.bind()
will bind
to the "all interfaces" address on a random port (it does the right thing for
both udp4
and udp6
sockets). You can then retrieve the address and port
with socket.address().address
and socket.address().port
.
Class: dgram.Socket#
The dgram Socket class encapsulates the datagram functionality. It
should be created via dgram.createSocket(...)
Event: 'message'#
msg
Buffer object. The messagerinfo
Object. Remote address information
Emitted when a new datagram is available on a socket. msg
is a Buffer
and
rinfo
is an object with the sender's address information:
socket.on('message', function(msg, rinfo) {
console.log('Received %d bytes from %s:%d\n',
msg.length, rinfo.address, rinfo.port);
});
Event: 'listening'#
Emitted when a socket starts listening for datagrams. This happens as soon as UDP sockets are created.
Event: 'close'#
Emitted when a socket is closed with close()
. No new message
events will be emitted
on this socket.
Event: 'error'#
exception
Error object
Emitted when an error occurs.
socket.send(buf, offset, length, port, address, [callback])#
buf
Buffer object or string. Message to be sentoffset
Integer. Offset in the buffer where the message starts.length
Integer. Number of bytes in the message.port
Integer. Destination port.address
String. Destination hostname or IP address.callback
Function. Called when the message has been sent. Optional.
For UDP sockets, the destination port and address must be specified. A string
may be supplied for the address
parameter, and it will be resolved with DNS.
If the address is omitted or is an empty string, '0.0.0.0'
or '::0'
is used
instead. Depending on the network configuration, those defaults may or may not
work; it's best to be explicit about the destination address.
If the socket has not been previously bound with a call to bind
, it gets
assigned a random port number and is bound to the "all interfaces" address
('0.0.0.0'
for udp4
sockets, '::0'
for udp6
sockets.)
An optional callback may be specified to detect DNS errors or for determining
when it's safe to reuse the buf
object. Note that DNS lookups delay the time
to send for at least one tick. The only way to know for sure that the datagram
has been sent is by using a callback.
With consideration for multi-byte characters, offset
and length
will
be calculated with respect to
byte length
and not the character position.
Example of sending a UDP packet to a random port on localhost
;
var dgram = require('dgram');
var message = new Buffer("Some bytes");
var client = dgram.createSocket("udp4");
client.send(message, 0, message.length, 41234, "localhost", function(err) {
client.close();
});
A Note about UDP datagram size
The maximum size of an IPv4/v6
datagram depends on the MTU
(Maximum Transmission Unit)
and on the Payload Length
field size.
The
Payload Length
field is16 bits
wide, which means that a normal payload cannot be larger than 64K octets including internet header and data (65,507 bytes = 65,535 − 8 bytes UDP header − 20 bytes IP header); this is generally true for loopback interfaces, but such long datagrams are impractical for most hosts and networks.The
MTU
is the largest size a given link layer technology can support for datagrams. For any link,IPv4
mandates a minimumMTU
of68
octets, while the recommendedMTU
for IPv4 is576
(typically recommended as theMTU
for dial-up type applications), whether they arrive whole or in fragments.For
IPv6
, the minimumMTU
is1280
octets, however, the mandatory minimum fragment reassembly buffer size is1500
octets. The value of68
octets is very small, since most current link layer technologies have a minimumMTU
of1500
(like Ethernet).
Note that it's impossible to know in advance the MTU of each link through which
a packet might travel, and that generally sending a datagram greater than
the (receiver) MTU
won't work (the packet gets silently dropped, without
informing the source that the data did not reach its intended recipient).
socket.bind(port, [address], [callback])#
port
Integeraddress
String, Optionalcallback
Function with no parameters, Optional. Callback when binding is done.
For UDP sockets, listen for datagrams on a named port
and optional
address
. If address
is not specified, the OS will try to listen on
all addresses. After binding is done, a "listening" event is emitted
and the callback
(if specified) is called. Specifying both a
"listening" event listener and callback
is not harmful but not very
useful.
A bound datagram socket keeps the node process running to receive datagrams.
If binding fails, an "error" event is generated. In rare case (e.g.
binding a closed socket), an Error
may be thrown by this method.
Example of a UDP server listening on port 41234:
var dgram = require("dgram");
var server = dgram.createSocket("udp4");
server.on("error", function (err) {
console.log("server error:\n" + err.stack);
server.close();
});
server.on("message", function (msg, rinfo) {
console.log("server got: " + msg + " from " +
rinfo.address + ":" + rinfo.port);
});
server.on("listening", function () {
var address = server.address();
console.log("server listening " +
address.address + ":" + address.port);
});
server.bind(41234);
// server listening 0.0.0.0:41234
socket.bind(options, [callback])#
options
Object - Required. Supports the following properties:port
Number - Required.address
String - Optional.exclusive
Boolean - Optional.
callback
Function - Optional.
The port
and address
properties of options
, as well as the optional
callback function, behave as they do on a call to
socket.bind(port, [address], [callback])
.
If exclusive
is false
(default), then cluster workers will use the same
underlying handle, allowing connection handling duties to be shared. When
exclusive
is true
, the handle is not shared, and attempted port sharing
results in an error. An example which listens on an exclusive port is
shown below.
socket.bind({
address: 'localhost',
port: 8000,
exclusive: true
});
socket.close()#
Close the underlying socket and stop listening for data on it.
socket.address()#
Returns an object containing the address information for a socket. For UDP sockets,
this object will contain address
, family
and port
.
socket.setBroadcast(flag)#
flag
Boolean
Sets or clears the SO_BROADCAST
socket option. When this option is set, UDP packets
may be sent to a local interface's broadcast address.
socket.setTTL(ttl)#
ttl
Integer
Sets the IP_TTL
socket option. TTL stands for "Time to Live," but in this context it
specifies the number of IP hops that a packet is allowed to go through. Each router or
gateway that forwards a packet decrements the TTL. If the TTL is decremented to 0 by a
router, it will not be forwarded. Changing TTL values is typically done for network
probes or when multicasting.
The argument to setTTL()
is a number of hops between 1 and 255. The default on most
systems is 64.
socket.setMulticastTTL(ttl)#
ttl
Integer
Sets the IP_MULTICAST_TTL
socket option. TTL stands for "Time to Live," but in this
context it specifies the number of IP hops that a packet is allowed to go through,
specifically for multicast traffic. Each router or gateway that forwards a packet
decrements the TTL. If the TTL is decremented to 0 by a router, it will not be forwarded.
The argument to setMulticastTTL()
is a number of hops between 0 and 255. The default on most
systems is 1.
socket.setMulticastLoopback(flag)#
flag
Boolean
Sets or clears the IP_MULTICAST_LOOP
socket option. When this option is set, multicast
packets will also be received on the local interface.
socket.addMembership(multicastAddress, [multicastInterface])#
multicastAddress
StringmulticastInterface
String, Optional
Tells the kernel to join a multicast group with IP_ADD_MEMBERSHIP
socket option.
If multicastInterface
is not specified, the OS will try to add membership to all valid
interfaces.
socket.dropMembership(multicastAddress, [multicastInterface])#
multicastAddress
StringmulticastInterface
String, Optional
Opposite of addMembership
- tells the kernel to leave a multicast group with
IP_DROP_MEMBERSHIP
socket option. This is automatically called by the kernel
when the socket is closed or process terminates, so most apps will never need to call
this.
If multicastInterface
is not specified, the OS will try to drop membership to all valid
interfaces.
socket.unref()#
Calling unref
on a socket will allow the program to exit if this is the only
active socket in the event system. If the socket is already unref
d calling
unref
again will have no effect.
socket.ref()#
Opposite of unref
, calling ref
on a previously unref
d socket will not
let the program exit if it's the only socket left (the default behavior). If
the socket is ref
d calling ref
again will have no effect.
DNS#
Stability: 3 - Stable
Use require('dns')
to access this module. All methods in the dns module
use C-Ares except for dns.lookup
which uses getaddrinfo(3)
in a thread
pool. C-Ares is much faster than getaddrinfo
but the system resolver is
more consistent with how other programs operate. When a user does
net.connect(80, 'google.com')
or http.get({ host: 'google.com' })
the
dns.lookup
method is used. Users who need to do a large number of lookups
quickly should use the methods that go through C-Ares.
Here is an example which resolves 'www.google.com'
then reverse
resolves the IP addresses which are returned.
var dns = require('dns');
dns.resolve4('www.google.com', function (err, addresses) {
if (err) throw err;
console.log('addresses: ' + JSON.stringify(addresses));
addresses.forEach(function (a) {
dns.reverse(a, function (err, hostnames) {
if (err) {
throw err;
}
console.log('reverse for ' + a + ': ' + JSON.stringify(hostnames));
});
});
});
dns.lookup(hostname, [options], callback)#
Resolves a hostname (e.g. 'google.com'
) into the first found A (IPv4) or
AAAA (IPv6) record. options
can be an object or integer. If options
is
not provided, then IP v4 and v6 addresses are both valid. If options
is
an integer, then it must be 4
or 6
.
Alternatively, options
can be an object containing two properties,
family
and hints
. Both properties are optional. If family
is provided,
it must be the integer 4
or 6
. If family
is not provided then IP v4
and v6 addresses are accepted. The hints
field, if present, should be one
or more of the supported getaddrinfo
flags. If hints
is not provided,
then no flags are passed to getaddrinfo
. Multiple flags can be passed
through hints
by logically OR
ing their values. An example usage of
options
is shown below.
{
family: 4,
hints: dns.ADDRCONFIG | dns.V4MAPPED
}
See supported getaddrinfo
flags below for
more information on supported flags.
The callback has arguments (err, address, family)
. The address
argument
is a string representation of a IP v4 or v6 address. The family
argument
is either the integer 4 or 6 and denotes the family of address
(not
necessarily the value initially passed to lookup
).
On error, err
is an Error
object, where err.code
is the error code.
Keep in mind that err.code
will be set to 'ENOENT'
not only when
the hostname does not exist but also when the lookup fails in other ways
such as no available file descriptors.
dns.lookupService(address, port, callback)#
Resolves the given address and port into a hostname and service using
getnameinfo
.
The callback has arguments (err, hostname, service)
. The hostname
and
service
arguments are strings (e.g. 'localhost'
and 'http'
respectively).
On error, err
is an Error
object, where err.code
is the error code.
dns.resolve(hostname, [rrtype], callback)#
Resolves a hostname (e.g. 'google.com'
) into an array of the record types
specified by rrtype.
Valid rrtypes are:
'A'
(IPV4 addresses, default)'AAAA'
(IPV6 addresses)'MX'
(mail exchange records)'TXT'
(text records)'SRV'
(SRV records)'PTR'
(used for reverse IP lookups)'NS'
(name server records)'CNAME'
(canonical name records)'SOA'
(start of authority record)
The callback has arguments (err, addresses)
. The type of each item
in addresses
is determined by the record type, and described in the
documentation for the corresponding lookup methods below.
On error, err
is an Error
object, where err.code
is
one of the error codes listed below.
dns.resolve4(hostname, callback)#
The same as dns.resolve()
, but only for IPv4 queries (A
records).
addresses
is an array of IPv4 addresses (e.g.
['74.125.79.104', '74.125.79.105', '74.125.79.106']
).
dns.resolve6(hostname, callback)#
The same as dns.resolve4()
except for IPv6 queries (an AAAA
query).
dns.resolveMx(hostname, callback)#
The same as dns.resolve()
, but only for mail exchange queries (MX
records).
addresses
is an array of MX records, each with a priority and an exchange
attribute (e.g. [{'priority': 10, 'exchange': 'mx.example.com'},...]
).
dns.resolveTxt(hostname, callback)#
The same as dns.resolve()
, but only for text queries (TXT
records).
addresses
is an 2-d array of the text records available for hostname
(e.g.,
[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]
). Each sub-array contains TXT chunks of
one record. Depending on the use case, the could be either joined together or
treated separately.
dns.resolveSrv(hostname, callback)#
The same as dns.resolve()
, but only for service records (SRV
records).
addresses
is an array of the SRV records available for hostname
. Properties
of SRV records are priority, weight, port, and name (e.g.,
[{'priority': 10, 'weight': 5, 'port': 21223, 'name': 'service.example.com'}, ...]
).
dns.resolveSoa(hostname, callback)#
The same as dns.resolve()
, but only for start of authority record queries
(SOA
record).
addresses
is an object with the following structure:
{
nsname: 'ns.example.com',
hostmaster: 'root.example.com',
serial: 2013101809,
refresh: 10000,
retry: 2400,
expire: 604800,
minttl: 3600
}
dns.resolveNs(hostname, callback)#
The same as dns.resolve()
, but only for name server records (NS
records).
addresses
is an array of the name server records available for hostname
(e.g., ['ns1.example.com', 'ns2.example.com']
).
dns.resolveCname(hostname, callback)#
The same as dns.resolve()
, but only for canonical name records (CNAME
records). addresses
is an array of the canonical name records available for
hostname
(e.g., ['bar.example.com']
).
dns.reverse(ip, callback)#
Reverse resolves an ip address to an array of hostnames.
The callback has arguments (err, hostnames)
.
On error, err
is an Error
object, where err.code
is
one of the error codes listed below.
dns.getServers()#
Returns an array of IP addresses as strings that are currently being used for resolution
dns.setServers(servers)#
Given an array of IP addresses as strings, set them as the servers to use for resolving
If you specify a port with the address it will be stripped, as the underlying library doesn't support that.
This will throw if you pass invalid input.
Error codes#
Each DNS query can return one of the following error codes:
dns.NODATA
: DNS server returned answer with no data.dns.FORMERR
: DNS server claims query was misformatted.dns.SERVFAIL
: DNS server returned general failure.dns.NOTFOUND
: Domain name not found.dns.NOTIMP
: DNS server does not implement requested operation.dns.REFUSED
: DNS server refused query.dns.BADQUERY
: Misformatted DNS query.dns.BADNAME
: Misformatted hostname.dns.BADFAMILY
: Unsupported address family.dns.BADRESP
: Misformatted DNS reply.dns.CONNREFUSED
: Could not contact DNS servers.dns.TIMEOUT
: Timeout while contacting DNS servers.dns.EOF
: End of file.dns.FILE
: Error reading file.dns.NOMEM
: Out of memory.dns.DESTRUCTION
: Channel is being destroyed.dns.BADSTR
: Misformatted string.dns.BADFLAGS
: Illegal flags specified.dns.NONAME
: Given hostname is not numeric.dns.BADHINTS
: Illegal hints flags specified.dns.NOTINITIALIZED
: c-ares library initialization not yet performed.dns.LOADIPHLPAPI
: Error loading iphlpapi.dll.dns.ADDRGETNETWORKPARAMS
: Could not find GetNetworkParams function.dns.CANCELLED
: DNS query cancelled.
Supported getaddrinfo flags#
The following flags can be passed as hints to dns.lookup
.
dns.ADDRCONFIG
: Returned address types are determined by the types of addresses supported by the current system. For example, IPv4 addresses are only returned if the current system has at least one IPv4 address configured. Loopback addresses are not considered.dns.V4MAPPED
: If the IPv6 family was specified, but no IPv6 addresses were found, then return IPv4 mapped IPv6 addresses.
HTTP#
Stability: 3 - Stable
To use the HTTP server and client one must require('http')
.
The HTTP interfaces in Node are designed to support many features of the protocol which have been traditionally difficult to use. In particular, large, possibly chunk-encoded, messages. The interface is careful to never buffer entire requests or responses--the user is able to stream data.
HTTP message headers are represented by an object like this:
{ 'content-length': '123',
'content-type': 'text/plain',
'connection': 'keep-alive',
'host': 'mysite.com',
'accept': '*/*' }
Keys are lowercased. Values are not modified.
In order to support the full spectrum of possible HTTP applications, Node's HTTP API is very low-level. It deals with stream handling and message parsing only. It parses a message into headers and body but it does not parse the actual headers or the body.
Defined headers that allow multiple values are concatenated with a ,
character, except for the set-cookie
and cookie
headers which are
represented as an array of values. Headers such as content-length
which can only have a single value are parsed accordingly, and only a
single value is represented on the parsed object.
The raw headers as they were received are retained in the rawHeaders
property, which is an array of [key, value, key2, value2, ...]
. For
example, the previous message header object might have a rawHeaders
list like the following:
[ 'ConTent-Length', '123456',
'content-LENGTH', '123',
'content-type', 'text/plain',
'CONNECTION', 'keep-alive',
'Host', 'mysite.com',
'accepT', '*/*' ]
http.METHODS#
- Array
A list of the HTTP methods that are supported by the parser.
http.STATUS_CODES#
- Object
A collection of all the standard HTTP response status codes, and the
short description of each. For example, http.STATUS_CODES[404] === 'Not
Found'
.
http.createServer([requestListener])#
Returns a new web server object.
The requestListener
is a function which is automatically
added to the 'request'
event.
http.createClient([port], [host])#
This function is deprecated; please use http.request() instead.
Constructs a new HTTP client. port
and host
refer to the server to be
connected to.
Class: http.Server#
This is an EventEmitter with the following events:
Event: 'request'#
function (request, response) { }
Emitted each time there is a request. Note that there may be multiple requests
per connection (in the case of keep-alive connections).
request
is an instance of http.IncomingMessage and response
is
an instance of http.ServerResponse.
Event: 'connection'#
function (socket) { }
When a new TCP stream is established. socket
is an object of type
net.Socket
. Usually users will not want to access this event. In
particular, the socket will not emit readable
events because of how
the protocol parser attaches to the socket. The socket
can also be
accessed at request.connection
.
Event: 'close'#
function () { }
Emitted when the server closes.
Event: 'checkContinue'#
function (request, response) { }
Emitted each time a request with an http Expect: 100-continue is received. If this event isn't listened for, the server will automatically respond with a 100 Continue as appropriate.
Handling this event involves calling response.writeContinue() if the client should continue to send the request body, or generating an appropriate HTTP response (e.g., 400 Bad Request) if the client should not continue to send the request body.
Note that when this event is emitted and handled, the request
event will
not be emitted.
Event: 'connect'#
function (request, socket, head) { }
Emitted each time a client requests a http CONNECT method. If this event isn't listened for, then clients requesting a CONNECT method will have their connections closed.
request
is the arguments for the http request, as it is in the request event.socket
is the network socket between the server and client.head
is an instance of Buffer, the first packet of the tunneling stream, this may be empty.
After this event is emitted, the request's socket will not have a data
event listener, meaning you will need to bind to it in order to handle data
sent to the server on that socket.
Event: 'upgrade'#
function (request, socket, head) { }
Emitted each time a client requests a http upgrade. If this event isn't listened for, then clients requesting an upgrade will have their connections closed.
request
is the arguments for the http request, as it is in the request event.socket
is the network socket between the server and client.head
is an instance of Buffer, the first packet of the upgraded stream, this may be empty.
After this event is emitted, the request's socket will not have a data
event listener, meaning you will need to bind to it in order to handle data
sent to the server on that socket.
Event: 'clientError'#
function (exception, socket) { }
If a client connection emits an 'error' event - it will forwarded here.
socket
is the net.Socket
object that the error originated from.
server.listen(port, [hostname], [backlog], [callback])#
Begin accepting connections on the specified port and hostname. If the
hostname is omitted, the server will accept connections directed to any
IPv4 address (INADDR_ANY
).
To listen to a unix socket, supply a filename instead of port and hostname.
Backlog is the maximum length of the queue of pending connections.
The actual length will be determined by your OS through sysctl settings such as
tcp_max_syn_backlog
and somaxconn
on linux. The default value of this
parameter is 511 (not 512).
This function is asynchronous. The last parameter callback
will be added as
a listener for the 'listening' event. See also net.Server.listen(port).
server.listen(path, [callback])#
Start a UNIX socket server listening for connections on the given path
.
This function is asynchronous. The last parameter callback
will be added as
a listener for the 'listening' event. See also net.Server.listen(path).
server.listen(handle, [callback])#
handle
Objectcallback
Function
The handle
object can be set to either a server or socket (anything
with an underlying _handle
member), or a {fd: <n>}
object.
This will cause the server to accept connections on the specified handle, but it is presumed that the file descriptor or handle has already been bound to a port or domain socket.
Listening on a file descriptor is not supported on Windows.
This function is asynchronous. The last parameter callback
will be added as
a listener for the 'listening' event.
See also net.Server.listen().
server.close([callback])#
Stops the server from accepting new connections. See net.Server.close().
server.maxHeadersCount#
Limits maximum incoming headers count, equal to 1000 by default. If set to 0 - no limit will be applied.
server.setTimeout(msecs, callback)#
msecs
Numbercallback
Function
Sets the timeout value for sockets, and emits a 'timeout'
event on
the Server object, passing the socket as an argument, if a timeout
occurs.
If there is a 'timeout'
event listener on the Server object, then it
will be called with the timed-out socket as an argument.
By default, the Server's timeout value is 2 minutes, and sockets are
destroyed automatically if they time out. However, if you assign a
callback to the Server's 'timeout'
event, then you are responsible
for handling socket timeouts.
server.timeout#
- Number Default = 120000 (2 minutes)
The number of milliseconds of inactivity before a socket is presumed to have timed out.
Note that the socket timeout logic is set up on connection, so changing this value only affects new connections to the server, not any existing connections.
Set to 0 to disable any kind of automatic timeout behavior on incoming connections.
Class: http.ServerResponse#
This object is created internally by a HTTP server--not by the user. It is
passed as the second parameter to the 'request'
event.
The response implements the Writable Stream interface. This is an EventEmitter with the following events:
Event: 'close'#
function () { }
Indicates that the underlying connection was terminated before response.end() was called or able to flush.
Event: 'finish'#
function () { }
Emitted when the response has been sent. More specifically, this event is emitted when the last segment of the response headers and body have been handed off to the operating system for transmission over the network. It does not imply that the client has received anything yet.
After this event, no more events will be emitted on the response object.
response.writeContinue()#
Sends a HTTP/1.1 100 Continue message to the client, indicating that
the request body should be sent. See the 'checkContinue' event on Server
.
response.writeHead(statusCode, [statusMessage], [headers])#
Sends a response header to the request. The status code is a 3-digit HTTP
status code, like 404
. The last argument, headers
, are the response headers.
Optionally one can give a human-readable statusMessage
as the second
argument.
Example:
var body = 'hello world';
response.writeHead(200, {
'Content-Length': body.length,
'Content-Type': 'text/plain' });
This method must only be called once on a message and it must be called before response.end() is called.
If you call response.write() or response.end() before calling this, the implicit/mutable headers will be calculated and call this function for you.
Note: that Content-Length is given in bytes not characters. The above example
works because the string 'hello world'
contains only single byte characters.
If the body contains higher coded characters then Buffer.byteLength()
should be used to determine the number of bytes in a given encoding.
And Node does not check whether Content-Length and the length of the body
which has been transmitted are equal or not.
response.setTimeout(msecs, callback)#
msecs
Numbercallback
Function
Sets the Socket's timeout value to msecs
. If a callback is
provided, then it is added as a listener on the 'timeout'
event on
the response object.
If no 'timeout'
listener is added to the request, the response, or
the server, then sockets are destroyed when they time out. If you
assign a handler on the request, the response, or the server's
'timeout'
events, then it is your responsibility to handle timed out
sockets.
response.statusCode#
When using implicit headers (not calling response.writeHead() explicitly), this property controls the status code that will be sent to the client when the headers get flushed.
Example:
response.statusCode = 404;
After response header was sent to the client, this property indicates the status code which was sent out.
response.statusMessage#
When using implicit headers (not calling response.writeHead()
explicitly), this property
controls the status message that will be sent to the client when the headers get
flushed. If this is left as undefined
then the standard message for the status
code will be used.
Example:
response.statusMessage = 'Not found';
After response header was sent to the client, this property indicates the status message which was sent out.
response.setHeader(name, value)#
Sets a single header value for implicit headers. If this header already exists in the to-be-sent headers, its value will be replaced. Use an array of strings here if you need to send multiple headers with the same name.
Example:
response.setHeader("Content-Type", "text/html");
or
response.setHeader("Set-Cookie", ["type=ninja", "language=javascript"]);
response.headersSent#
Boolean (read-only). True if headers were sent, false otherwise.
response.sendDate#
When true, the Date header will be automatically generated and sent in the response if it is not already present in the headers. Defaults to true.
This should only be disabled for testing; HTTP requires the Date header in responses.
response.getHeader(name)#
Reads out a header that's already been queued but not sent to the client. Note that the name is case insensitive. This can only be called before headers get implicitly flushed.
Example:
var contentType = response.getHeader('content-type');
response.removeHeader(name)#
Removes a header that's queued for implicit sending.
Example:
response.removeHeader("Content-Encoding");
response.write(chunk, [encoding])#
If this method is called and response.writeHead() has not been called, it will switch to implicit header mode and flush the implicit headers.
This sends a chunk of the response body. This method may be called multiple times to provide successive parts of the body.
chunk
can be a string or a buffer. If chunk
is a string,
the second parameter specifies how to encode it into a byte stream.
By default the encoding
is 'utf8'
.
Note: This is the raw HTTP body and has nothing to do with higher-level multi-part body encodings that may be used.
The first time response.write()
is called, it will send the buffered
header information and the first body to the client. The second time
response.write()
is called, Node assumes you're going to be streaming
data, and sends that separately. That is, the response is buffered up to the
first chunk of body.
Returns true
if the entire data was flushed successfully to the kernel
buffer. Returns false
if all or part of the data was queued in user memory.
'drain'
will be emitted when the buffer is again free.
response.addTrailers(headers)#
This method adds HTTP trailing headers (a header but at the end of the message) to the response.
Trailers will only be emitted if chunked encoding is used for the response; if it is not (e.g., if the request was HTTP/1.0), they will be silently discarded.
Note that HTTP requires the Trailer
header to be sent if you intend to
emit trailers, with a list of the header fields in its value. E.g.,
response.writeHead(200, { 'Content-Type': 'text/plain',
'Trailer': 'Content-MD5' });
response.write(fileData);
response.addTrailers({'Content-MD5': "7895bf4b8828b55ceaf47747b4bca667"});
response.end();
response.end([data], [encoding])#
This method signals to the server that all of the response headers and body
have been sent; that server should consider this message complete.
The method, response.end()
, MUST be called on each
response.
If data
is specified, it is equivalent to calling response.write(data, encoding)
followed by response.end()
.
http.request(options, [callback])#
Node maintains several connections per server to make HTTP requests. This function allows one to transparently issue requests.
options
can be an object or a string. If options
is a string, it is
automatically parsed with url.parse().
Options:
host
: A domain name or IP address of the server to issue the request to. Defaults to'localhost'
.hostname
: To supporturl.parse()
hostname
is preferred overhost
port
: Port of remote server. Defaults to 80.localAddress
: Local interface to bind for network connections.socketPath
: Unix Domain Socket (use one of host:port or socketPath)method
: A string specifying the HTTP request method. Defaults to'GET'
.path
: Request path. Defaults to'/'
. Should include query string if any. E.G.'/index.html?page=12'
. An exception is thrown when the request path contains illegal characters. Currently, only spaces are rejected but that may change in the future.headers
: An object containing request headers.auth
: Basic authentication i.e.'user:password'
to compute an Authorization header.agent
: Controls Agent behavior. When an Agent is used request will default toConnection: keep-alive
. Possible values:undefined
(default): use global Agent for this host and port.Agent
object: explicitly use the passed inAgent
.false
: opts out of connection pooling with an Agent, defaults request toConnection: close
.
keepAlive
: {Boolean} Keep sockets around in a pool to be used by other requests in the future. Default =false
keepAliveMsecs
: {Integer} When using HTTP KeepAlive, how often to send TCP KeepAlive packets over sockets being kept alive. Default =1000
. Only relevant ifkeepAlive
is set totrue
.
The optional callback
parameter will be added as a one time listener for
the 'response' event.
http.request()
returns an instance of the http.ClientRequest
class. The ClientRequest
instance is a writable stream. If one needs to
upload a file with a POST request, then write to the ClientRequest
object.
Example:
var postData = querystring.stringify({
'msg' : 'Hello World!'
});
var options = {
hostname: 'www.google.com',
port: 80,
path: '/upload',
method: 'POST',
headers: {
'Content-Type': 'application/x-www-form-urlencoded',
'Content-Length': postData.length
}
};
var req = http.request(options, function(res) {
console.log('STATUS: ' + res.statusCode);
console.log('HEADERS: ' + JSON.stringify(res.headers));
res.setEncoding('utf8');
res.on('data', function (chunk) {
console.log('BODY: ' + chunk);
});
});
req.on('error', function(e) {
console.log('problem with request: ' + e.message);
});
// write data to request body
req.write(postData);
req.end();
Note that in the example req.end()
was called. With http.request()
one
must always call req.end()
to signify that you're done with the request -
even if there is no data being written to the request body.
If any error is encountered during the request (be that with DNS resolution,
TCP level errors, or actual HTTP parse errors) an 'error'
event is emitted
on the returned request object.
There are a few special headers that should be noted.
Sending a 'Connection: keep-alive' will notify Node that the connection to the server should be persisted until the next request.
Sending a 'Content-length' header will disable the default chunked encoding.
Sending an 'Expect' header will immediately send the request headers. Usually, when sending 'Expect: 100-continue', you should both set a timeout and listen for the
continue
event. See RFC2616 Section 8.2.3 for more information.Sending an Authorization header will override using the
auth
option to compute basic authentication.
http.get(options, [callback])#
Since most requests are GET requests without bodies, Node provides this
convenience method. The only difference between this method and http.request()
is that it sets the method to GET and calls req.end()
automatically.
Example:
http.get("http://www.google.com/index.html", function(res) {
console.log("Got response: " + res.statusCode);
}).on('error', function(e) {
console.log("Got error: " + e.message);
});
Class: http.Agent#
The HTTP Agent is used for pooling sockets used in HTTP client requests.
The HTTP Agent also defaults client requests to using Connection:keep-alive. If no pending HTTP requests are waiting on a socket to become free the socket is closed. This means that Node's pool has the benefit of keep-alive when under load but still does not require developers to manually close the HTTP clients using KeepAlive.
If you opt into using HTTP KeepAlive, you can create an Agent object
with that flag set to true
. (See the constructor
options below.) Then, the Agent will keep
unused sockets in a pool for later use. They will be explicitly
marked so as to not keep the Node process running. However, it is
still a good idea to explicitly destroy()
KeepAlive agents when they are no longer in use, so that the Sockets
will be shut down.
Sockets are removed from the agent's pool when the socket emits either a "close" event or a special "agentRemove" event. This means that if you intend to keep one HTTP request open for a long time and don't want it to stay in the pool you can do something along the lines of:
http.get(options, function(res) {
// Do stuff
}).on("socket", function (socket) {
socket.emit("agentRemove");
});
Alternatively, you could just opt out of pooling entirely using
agent:false
:
http.get({
hostname: 'localhost',
port: 80,
path: '/',
agent: false // create a new agent just for this one request
}, function (res) {
// Do stuff with response
})
new Agent([options])#
options
Object Set of configurable options to set on the agent. Can have the following fields:keepAlive
Boolean Keep sockets around in a pool to be used by other requests in the future. Default =false
keepAliveMsecs
Integer When using HTTP KeepAlive, how often to send TCP KeepAlive packets over sockets being kept alive. Default =1000
. Only relevant ifkeepAlive
is set totrue
.maxSockets
Number Maximum number of sockets to allow per host. Default =Infinity
.maxFreeSockets
Number Maximum number of sockets to leave open in a free state. Only relevant ifkeepAlive
is set totrue
. Default =256
.
The default http.globalAgent
that is used by http.request
has all
of these values set to their respective defaults.
To configure any of them, you must create your own Agent
object.
var http = require('http');
var keepAliveAgent = new http.Agent({ keepAlive: true });
options.agent = keepAliveAgent;
http.request(options, onResponseCallback);
agent.maxSockets#
By default set to Infinity. Determines how many concurrent sockets the agent can have open per origin. Origin is either a 'host:port' or 'host:port:localAddress' combination.
agent.maxFreeSockets#
By default set to 256. For Agents supporting HTTP KeepAlive, this sets the maximum number of sockets that will be left open in the free state.
agent.sockets#
An object which contains arrays of sockets currently in use by the Agent. Do not modify.
agent.freeSockets#
An object which contains arrays of sockets currently awaiting use by the Agent when HTTP KeepAlive is used. Do not modify.
agent.requests#
An object which contains queues of requests that have not yet been assigned to sockets. Do not modify.
agent.destroy()#
Destroy any sockets that are currently in use by the agent.
It is usually not necessary to do this. However, if you are using an agent with KeepAlive enabled, then it is best to explicitly shut down the agent when you know that it will no longer be used. Otherwise, sockets may hang open for quite a long time before the server terminates them.
agent.getName(options)#
Get a unique name for a set of request options, to determine whether a
connection can be reused. In the http agent, this returns
host:port:localAddress
. In the https agent, the name includes the
CA, cert, ciphers, and other HTTPS/TLS-specific options that determine
socket reusability.
http.globalAgent#
Global instance of Agent which is used as the default for all http client requests.
Class: http.ClientRequest#
This object is created internally and returned from http.request()
. It
represents an in-progress request whose header has already been queued. The
header is still mutable using the setHeader(name, value)
, getHeader(name)
,
removeHeader(name)
API. The actual header will be sent along with the first
data chunk or when closing the connection.
To get the response, add a listener for 'response'
to the request object.
'response'
will be emitted from the request object when the response
headers have been received. The 'response'
event is executed with one
argument which is an instance of http.IncomingMessage.
During the 'response'
event, one can add listeners to the
response object; particularly to listen for the 'data'
event.
If no 'response'
handler is added, then the response will be
entirely discarded. However, if you add a 'response'
event handler,
then you must consume the data from the response object, either by
calling response.read()
whenever there is a 'readable'
event, or
by adding a 'data'
handler, or by calling the .resume()
method.
Until the data is consumed, the 'end'
event will not fire. Also, until
the data is read it will consume memory that can eventually lead to a
'process out of memory' error.
Note: Node does not check whether Content-Length and the length of the body which has been transmitted are equal or not.
The request implements the Writable Stream interface. This is an EventEmitter with the following events:
Event: 'response'#
function (response) { }
Emitted when a response is received to this request. This event is emitted only
once. The response
argument will be an instance of http.IncomingMessage.
Options:
host
: A domain name or IP address of the server to issue the request to.port
: Port of remote server.socketPath
: Unix Domain Socket (use one of host:port or socketPath)
Event: 'socket'#
function (socket) { }
Emitted after a socket is assigned to this request.
Event: 'connect'#
function (response, socket, head) { }
Emitted each time a server responds to a request with a CONNECT method. If this event isn't being listened for, clients receiving a CONNECT method will have their connections closed.
A client server pair that show you how to listen for the connect
event.
var http = require('http');
var net = require('net');
var url = require('url');
// Create an HTTP tunneling proxy
var proxy = http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('okay');
});
proxy.on('connect', function(req, cltSocket, head) {
// connect to an origin server
var srvUrl = url.parse('http://' + req.url);
var srvSocket = net.connect(srvUrl.port, srvUrl.hostname, function() {
cltSocket.write('HTTP/1.1 200 Connection Established\r\n' +
'Proxy-agent: Node-Proxy\r\n' +
'\r\n');
srvSocket.write(head);
srvSocket.pipe(cltSocket);
cltSocket.pipe(srvSocket);
});
});
// now that proxy is running
proxy.listen(1337, '127.0.0.1', function() {
// make a request to a tunneling proxy
var options = {
port: 1337,
hostname: '127.0.0.1',
method: 'CONNECT',
path: 'www.google.com:80'
};
var req = http.request(options);
req.end();
req.on('connect', function(res, socket, head) {
console.log('got connected!');
// make a request over an HTTP tunnel
socket.write('GET / HTTP/1.1\r\n' +
'Host: www.google.com:80\r\n' +
'Connection: close\r\n' +
'\r\n');
socket.on('data', function(chunk) {
console.log(chunk.toString());
});
socket.on('end', function() {
proxy.close();
});
});
});
Event: 'upgrade'#
function (response, socket, head) { }
Emitted each time a server responds to a request with an upgrade. If this event isn't being listened for, clients receiving an upgrade header will have their connections closed.
A client server pair that show you how to listen for the upgrade
event.
var http = require('http');
// Create an HTTP server
var srv = http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('okay');
});
srv.on('upgrade', function(req, socket, head) {
socket.write('HTTP/1.1 101 Web Socket Protocol Handshake\r\n' +
'Upgrade: WebSocket\r\n' +
'Connection: Upgrade\r\n' +
'\r\n');
socket.pipe(socket); // echo back
});
// now that server is running
srv.listen(1337, '127.0.0.1', function() {
// make a request
var options = {
port: 1337,
hostname: '127.0.0.1',
headers: {
'Connection': 'Upgrade',
'Upgrade': 'websocket'
}
};
var req = http.request(options);
req.end();
req.on('upgrade', function(res, socket, upgradeHead) {
console.log('got upgraded!');
socket.end();
process.exit(0);
});
});
Event: 'continue'#
function () { }
Emitted when the server sends a '100 Continue' HTTP response, usually because the request contained 'Expect: 100-continue'. This is an instruction that the client should send the request body.
request.flush()#
Flush the request headers.
For efficiency reasons, node.js normally buffers the request headers until you
call request.end()
or write the first chunk of request data. It then tries
hard to pack the request headers and data into a single TCP packet.
That's usually what you want (it saves a TCP round-trip) but not when the first
data isn't sent until possibly much later. request.flush()
lets you bypass
the optimization and kickstart the request.
request.write(chunk, [encoding])#
Sends a chunk of the body. By calling this method
many times, the user can stream a request body to a
server--in that case it is suggested to use the
['Transfer-Encoding', 'chunked']
header line when
creating the request.
The chunk
argument should be a Buffer or a string.
The encoding
argument is optional and only applies when chunk
is a string.
Defaults to 'utf8'
.
request.end([data], [encoding])#
Finishes sending the request. If any parts of the body are
unsent, it will flush them to the stream. If the request is
chunked, this will send the terminating '0\r\n\r\n'
.
If data
is specified, it is equivalent to calling
request.write(data, encoding)
followed by request.end()
.
request.abort()#
Aborts a request. (New since v0.3.8.)
request.setTimeout(timeout, [callback])#
Once a socket is assigned to this request and is connected socket.setTimeout() will be called.
request.setNoDelay([noDelay])#
Once a socket is assigned to this request and is connected socket.setNoDelay() will be called.
request.setSocketKeepAlive([enable], [initialDelay])#
Once a socket is assigned to this request and is connected socket.setKeepAlive() will be called.
http.IncomingMessage#
An IncomingMessage
object is created by http.Server or
http.ClientRequest and passed as the first argument to the 'request'
and 'response'
event respectively. It may be used to access response status,
headers and data.
It implements the Readable Stream interface, as well as the following additional events, methods, and properties.
Event: 'close'#
function () { }
Indicates that the underlaying connection was closed.
Just like 'end'
, this event occurs only once per response.
message.httpVersion#
In case of server request, the HTTP version sent by the client. In the case of
client response, the HTTP version of the connected-to server.
Probably either '1.1'
or '1.0'
.
Also response.httpVersionMajor
is the first integer and
response.httpVersionMinor
is the second.
message.headers#
The request/response headers object.
Read only map of header names and values. Header names are lower-cased. Example:
// Prints something like:
//
// { 'user-agent': 'curl/7.22.0',
// host: '127.0.0.1:8000',
// accept: '*/*' }
console.log(request.headers);
message.rawHeaders#
The raw request/response headers list exactly as they were received.
Note that the keys and values are in the same list. It is not a list of tuples. So, the even-numbered offsets are key values, and the odd-numbered offsets are the associated values.
Header names are not lowercased, and duplicates are not merged.
// Prints something like:
//
// [ 'user-agent',
// 'this is invalid because there can be only one',
// 'User-Agent',
// 'curl/7.22.0',
// 'Host',
// '127.0.0.1:8000',
// 'ACCEPT',
// '*/*' ]
console.log(request.rawHeaders);
message.trailers#
The request/response trailers object. Only populated at the 'end' event.
message.rawTrailers#
The raw request/response trailer keys and values exactly as they were received. Only populated at the 'end' event.
message.setTimeout(msecs, callback)#
msecs
Numbercallback
Function
Calls message.connection.setTimeout(msecs, callback)
.
message.method#
Only valid for request obtained from http.Server.
The request method as a string. Read only. Example:
'GET'
, 'DELETE'
.
message.url#
Only valid for request obtained from http.Server.
Request URL string. This contains only the URL that is present in the actual HTTP request. If the request is:
GET /status?name=ryan HTTP/1.1\r\n
Accept: text/plain\r\n
\r\n
Then request.url
will be:
'/status?name=ryan'
If you would like to parse the URL into its parts, you can use
require('url').parse(request.url)
. Example:
node> require('url').parse('/status?name=ryan')
{ href: '/status?name=ryan',
search: '?name=ryan',
query: 'name=ryan',
pathname: '/status' }
If you would like to extract the params from the query string,
you can use the require('querystring').parse
function, or pass
true
as the second argument to require('url').parse
. Example:
node> require('url').parse('/status?name=ryan', true)
{ href: '/status?name=ryan',
search: '?name=ryan',
query: { name: 'ryan' },
pathname: '/status' }
message.statusCode#
Only valid for response obtained from http.ClientRequest
.
The 3-digit HTTP response status code. E.G. 404
.
message.statusMessage#
Only valid for response obtained from http.ClientRequest
.
The HTTP response status message (reason phrase). E.G. OK
or Internal Server Error
.
message.socket#
The net.Socket
object associated with the connection.
With HTTPS support, use request.connection.verifyPeer() and request.connection.getPeerCertificate() to obtain the client's authentication details.
HTTPS#
Stability: 3 - Stable
HTTPS is the HTTP protocol over TLS/SSL. In Node this is implemented as a separate module.
Class: https.Server#
This class is a subclass of tls.Server
and emits events same as
http.Server
. See http.Server
for more information.
server.setTimeout(msecs, callback)#
server.timeout#
See http.Server#timeout.
https.createServer(options, [requestListener])#
Returns a new HTTPS web server object. The options
is similar to
tls.createServer(). The requestListener
is a function which is
automatically added to the 'request'
event.
Example:
// curl -k https://localhost:8000/
var https = require('https');
var fs = require('fs');
var options = {
key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),
cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')
};
https.createServer(options, function (req, res) {
res.writeHead(200);
res.end("hello world\n");
}).listen(8000);
Or
var https = require('https');
var fs = require('fs');
var options = {
pfx: fs.readFileSync('server.pfx')
};
https.createServer(options, function (req, res) {
res.writeHead(200);
res.end("hello world\n");
}).listen(8000);
server.listen(port, [host], [backlog], [callback])#
server.listen(path, [callback])#
server.listen(handle, [callback])#
See http.listen() for details.
server.close([callback])#
See http.close() for details.
https.request(options, callback)#
Makes a request to a secure web server.
options
can be an object or a string. If options
is a string, it is
automatically parsed with url.parse().
All options from http.request() are valid.
Example:
var https = require('https');
var options = {
hostname: 'encrypted.google.com',
port: 443,
path: '/',
method: 'GET'
};
var req = https.request(options, function(res) {
console.log("statusCode: ", res.statusCode);
console.log("headers: ", res.headers);
res.on('data', function(d) {
process.stdout.write(d);
});
});
req.end();
req.on('error', function(e) {
console.error(e);
});
The options argument has the following options
host
: A domain name or IP address of the server to issue the request to. Defaults to'localhost'
.hostname
: To supporturl.parse()
hostname
is preferred overhost
port
: Port of remote server. Defaults to 443.method
: A string specifying the HTTP request method. Defaults to'GET'
.path
: Request path. Defaults to'/'
. Should include query string if any. E.G.'/index.html?page=12'
headers
: An object containing request headers.auth
: Basic authentication i.e.'user:password'
to compute an Authorization header.agent
: Controls Agent behavior. When an Agent is used request will default toConnection: keep-alive
. Possible values:undefined
(default): use globalAgent for this host and port.Agent
object: explicitly use the passed inAgent
.false
: opts out of connection pooling with an Agent, defaults request toConnection: close
.
The following options from tls.connect() can also be specified. However, a globalAgent silently ignores these.
pfx
: Certificate, Private key and CA certificates to use for SSL. Defaultnull
.key
: Private key to use for SSL. Defaultnull
.passphrase
: A string of passphrase for the private key or pfx. Defaultnull
.cert
: Public x509 certificate to use. Defaultnull
.ca
: An authority certificate or array of authority certificates to check the remote host against.ciphers
: A string describing the ciphers to use or exclude. Consult http://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT for details on the format.rejectUnauthorized
: Iftrue
, the server certificate is verified against the list of supplied CAs. An'error'
event is emitted if verification fails. Verification happens at the connection level, before the HTTP request is sent. Defaulttrue
.secureProtocol
: The SSL method to use, e.g.SSLv3_method
to force SSL version 3. The possible values depend on your installation of OpenSSL and are defined in the constant SSL_METHODS.
In order to specify these options, use a custom Agent
.
Example:
var options = {
hostname: 'encrypted.google.com',
port: 443,
path: '/',
method: 'GET',
key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),
cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')
};
options.agent = new https.Agent(options);
var req = https.request(options, function(res) {
...
}
Or does not use an Agent
.
Example:
var options = {
hostname: 'encrypted.google.com',
port: 443,
path: '/',
method: 'GET',
key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),
cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem'),
agent: false
};
var req = https.request(options, function(res) {
...
}
https.get(options, callback)#
Like http.get()
but for HTTPS.
options
can be an object or a string. If options
is a string, it is
automatically parsed with url.parse().
Example:
var https = require('https');
https.get('https://encrypted.google.com/', function(res) {
console.log("statusCode: ", res.statusCode);
console.log("headers: ", res.headers);
res.on('data', function(d) {
process.stdout.write(d);
});
}).on('error', function(e) {
console.error(e);
});
Class: https.Agent#
An Agent object for HTTPS similar to http.Agent. See https.request() for more information.
https.globalAgent#
Global instance of https.Agent for all HTTPS client requests.
URL#
Stability: 3 - Stable
This module has utilities for URL resolution and parsing.
Call require('url')
to use it.
Parsed URL objects have some or all of the following fields, depending on whether or not they exist in the URL string. Any parts that are not in the URL string will not be in the parsed object. Examples are shown for the URL
'http://user:[email protected]:8080/p/a/t/h?query=string#hash'
href
: The full URL that was originally parsed. Both the protocol and host are lowercased.Example:
'http://user:[email protected]:8080/p/a/t/h?query=string#hash'
protocol
: The request protocol, lowercased.Example:
'http:'
slashes
: The protocol requires slashes after the colonExample: true or false
host
: The full lowercased host portion of the URL, including port information.Example:
'host.com:8080'
auth
: The authentication information portion of a URL.Example:
'user:pass'
hostname
: Just the lowercased hostname portion of the host.Example:
'host.com'
port
: The port number portion of the host.Example:
'8080'
pathname
: The path section of the URL, that comes after the host and before the query, including the initial slash if present.Example:
'/p/a/t/h'
search
: The 'query string' portion of the URL, including the leading question mark.Example:
'?query=string'
path
: Concatenation ofpathname
andsearch
.Example:
'/p/a/t/h?query=string'
query
: Either the 'params' portion of the query string, or a querystring-parsed object.Example:
'query=string'
or{'query':'string'}
hash
: The 'fragment' portion of the URL including the pound-sign.Example:
'#hash'
The following methods are provided by the URL module:
url.parse(urlStr, [parseQueryString], [slashesDenoteHost])#
Take a URL string, and return an object.
Pass true
as the second argument to also parse
the query string using the querystring
module.
Defaults to false
.
Pass true
as the third argument to treat //foo/bar
as
{ host: 'foo', pathname: '/bar' }
rather than
{ pathname: '//foo/bar' }
. Defaults to false
.
url.format(urlObj)#
Take a parsed URL object, and return a formatted URL string.
href
will be ignored.protocol
is treated the same with or without the trailing:
(colon).- The protocols
http
,https
,ftp
,gopher
,file
will be postfixed with://
(colon-slash-slash). - All other protocols
mailto
,xmpp
,aim
,sftp
,foo
, etc will be postfixed with:
(colon)
- The protocols
slashes
set totrue
if the protocol requires://
(colon-slash-slash)- Only needs to be set for protocols not previously listed as requiring
slashes, such as
mongodb://localhost:8000/
- Only needs to be set for protocols not previously listed as requiring
slashes, such as
auth
will be used if present.hostname
will only be used ifhost
is absent.port
will only be used ifhost
is absent.host
will be used in place ofhostname
andport
pathname
is treated the same with or without the leading/
(slash)search
will be used in place ofquery
query
(object; seequerystring
) will only be used ifsearch
is absent.search
is treated the same with or without the leading?
(question mark)hash
is treated the same with or without the leading#
(pound sign, anchor)
url.resolve(from, to)#
Take a base URL, and a href URL, and resolve them as a browser would for an anchor tag. Examples:
url.resolve('/one/two/three', 'four') // '/one/two/four'
url.resolve('http://example.com/', '/one') // 'http://example.com/one'
url.resolve('http://example.com/one', '/two') // 'http://example.com/two'
Query String#
Stability: 3 - Stable
This module provides utilities for dealing with query strings. It provides the following methods:
querystring.stringify(obj, [sep], [eq], [options])#
Serialize an object to a query string.
Optionally override the default separator ('&'
) and assignment ('='
)
characters.
Options object may contain encodeURIComponent
property (querystring.escape
by default),
it can be used to encode string with non-utf8
encoding if necessary.
Example:
querystring.stringify({ foo: 'bar', baz: ['qux', 'quux'], corge: '' })
// returns
'foo=bar&baz=qux&baz=quux&corge='
querystring.stringify({foo: 'bar', baz: 'qux'}, ';', ':')
// returns
'foo:bar;baz:qux'
// Suppose gbkEncodeURIComponent function already exists,
// it can encode string with `gbk` encoding
querystring.stringify({ w: '中文', foo: 'bar' }, null, null,
{ encodeURIComponent: gbkEncodeURIComponent })
// returns
'w=%D6%D0%CE%C4&foo=bar'
querystring.parse(str, [sep], [eq], [options])#
Deserialize a query string to an object.
Optionally override the default separator ('&'
) and assignment ('='
)
characters.
Options object may contain maxKeys
property (equal to 1000 by default), it'll
be used to limit processed keys. Set it to 0 to remove key count limitation.
Options object may contain decodeURIComponent
property (decodeURIComponent
by default),
it can be used to decode non-utf8
encoding string if necessary.
Example:
querystring.parse('foo=bar&baz=qux&baz=quux&corge')
// returns
{ foo: 'bar', baz: ['qux', 'quux'], corge: '' }
// Suppose gbkDecodeURIComponent function already exists,
// it can decode `gbk` encoding string
querystring.parse('w=%D6%D0%CE%C4&foo=bar', null, null,
{ decodeURIComponent: gbkDecodeURIComponent })
// returns
{ w: '中文', foo: 'bar' }
querystring.escape#
The escape function used by querystring.stringify
,
provided so that it could be overridden if necessary.
querystring.unescape#
The unescape function used by querystring.parse
,
provided so that it could be overridden if necessary.
punycode#
Stability: 2 - Unstable
Punycode.js is bundled with Node.js v0.6.2+. Use
require('punycode')
to access it. (To use it with other Node.js versions,
use npm to install the punycode
module first.)
punycode.decode(string)#
Converts a Punycode string of ASCII-only symbols to a string of Unicode symbols.
// decode domain name parts
punycode.decode('maana-pta'); // 'mañana'
punycode.decode('--dqo34k'); // '☃-⌘'
punycode.encode(string)#
Converts a string of Unicode symbols to a Punycode string of ASCII-only symbols.
// encode domain name parts
punycode.encode('mañana'); // 'maana-pta'
punycode.encode('☃-⌘'); // '--dqo34k'
punycode.toUnicode(domain)#
Converts a Punycode string representing a domain name to Unicode. Only the Punycoded parts of the domain name will be converted, i.e. it doesn't matter if you call it on a string that has already been converted to Unicode.
// decode domain names
punycode.toUnicode('xn--maana-pta.com'); // 'mañana.com'
punycode.toUnicode('xn----dqo34k.com'); // '☃-⌘.com'
punycode.toASCII(domain)#
Converts a Unicode string representing a domain name to Punycode. Only the non-ASCII parts of the domain name will be converted, i.e. it doesn't matter if you call it with a domain that's already in ASCII.
// encode domain names
punycode.toASCII('mañana.com'); // 'xn--maana-pta.com'
punycode.toASCII('☃-⌘.com'); // 'xn----dqo34k.com'
punycode.ucs2#
punycode.ucs2.decode(string)#
Creates an array containing the numeric code point values of each Unicode symbol in the string. While JavaScript uses UCS-2 internally, this function will convert a pair of surrogate halves (each of which UCS-2 exposes as separate characters) into a single code point, matching UTF-16.
punycode.ucs2.decode('abc'); // [0x61, 0x62, 0x63]
// surrogate pair for U+1D306 tetragram for centre:
punycode.ucs2.decode('\uD834\uDF06'); // [0x1D306]
punycode.ucs2.encode(codePoints)#
Creates a string based on an array of numeric code point values.
punycode.ucs2.encode([0x61, 0x62, 0x63]); // 'abc'
punycode.ucs2.encode([0x1D306]); // '\uD834\uDF06'
punycode.version#
A string representing the current Punycode.js version number.
Readline#
Stability: 2 - Unstable
To use this module, do require('readline')
. Readline allows reading of a
stream (such as process.stdin
) on a line-by-line basis.
Note that once you've invoked this module, your node program will not terminate until you've closed the interface. Here's how to allow your program to gracefully exit:
var readline = require('readline');
var rl = readline.createInterface({
input: process.stdin,
output: process.stdout
});
rl.question("What do you think of node.js? ", function(answer) {
// TODO: Log the answer in a database
console.log("Thank you for your valuable feedback:", answer);
rl.close();
});
readline.createInterface(options)#
Creates a readline Interface
instance. Accepts an "options" Object that takes
the following values:
input
- the readable stream to listen to (Required).output
- the writable stream to write readline data to (Required).completer
- an optional function that is used for Tab autocompletion. See below for an example of using this.terminal
- passtrue
if theinput
andoutput
streams should be treated like a TTY, and have ANSI/VT100 escape codes written to it. Defaults to checkingisTTY
on theoutput
stream upon instantiation.
The completer
function is given the current line entered by the user, and
is supposed to return an Array with 2 entries:
An Array with matching entries for the completion.
The substring that was used for the matching.
Which ends up looking something like:
[[substr1, substr2, ...], originalsubstring]
.
Example:
function completer(line) {
var completions = '.help .error .exit .quit .q'.split(' ')
var hits = completions.filter(function(c) { return c.indexOf(line) == 0 })
// show all completions if none found
return [hits.length ? hits : completions, line]
}
Also completer
can be run in async mode if it accepts two arguments:
function completer(linePartial, callback) {
callback(null, [['123'], linePartial]);
}
createInterface
is commonly used with process.stdin
and
process.stdout
in order to accept user input:
var readline = require('readline');
var rl = readline.createInterface({
input: process.stdin,
output: process.stdout
});
Once you have a readline instance, you most commonly listen for the
"line"
event.
If terminal
is true
for this instance then the output
stream will get
the best compatibility if it defines an output.columns
property, and fires
a "resize"
event on the output
if/when the columns ever change
(process.stdout
does this automatically when it is a TTY).
Class: Interface#
The class that represents a readline interface with an input and output stream.
rl.setPrompt(prompt)#
Sets the prompt, for example when you run node
on the command line, you see
>
, which is node's prompt.
rl.prompt([preserveCursor])#
Readies readline for input from the user, putting the current setPrompt
options on a new line, giving the user a new spot to write. Set preserveCursor
to true
to prevent the cursor placement being reset to 0
.
This will also resume the input
stream used with createInterface
if it has
been paused.
rl.question(query, callback)#
Prepends the prompt with query
and invokes callback
with the user's
response. Displays the query to the user, and then invokes callback
with the user's response after it has been typed.
This will also resume the input
stream used with createInterface
if
it has been paused.
Example usage:
interface.question('What is your favorite food?', function(answer) {
console.log('Oh, so your favorite food is ' + answer);
});
rl.pause()#
Pauses the readline input
stream, allowing it to be resumed later if needed.
rl.resume()#
Resumes the readline input
stream.
rl.close()#
Closes the Interface
instance, relinquishing control on the input
and
output
streams. The "close" event will also be emitted.
rl.write(data, [key])#
Writes data
to output
stream. key
is an object literal to represent a key
sequence; available if the terminal is a TTY.
This will also resume the input
stream if it has been paused.
Example:
rl.write('Delete me!');
// Simulate ctrl+u to delete the line written previously
rl.write(null, {ctrl: true, name: 'u'});
Events#
Event: 'line'#
function (line) {}
Emitted whenever the input
stream receives a \n
, usually received when the
user hits enter, or return. This is a good hook to listen for user input.
Example of listening for line
:
rl.on('line', function (cmd) {
console.log('You just typed: '+cmd);
});
Event: 'pause'#
function () {}
Emitted whenever the input
stream is paused.
Also emitted whenever the input
stream is not paused and receives the
SIGCONT
event. (See events SIGTSTP
and SIGCONT
)
Example of listening for pause
:
rl.on('pause', function() {
console.log('Readline paused.');
});
Event: 'resume'#
function () {}
Emitted whenever the input
stream is resumed.
Example of listening for resume
:
rl.on('resume', function() {
console.log('Readline resumed.');
});
Event: 'close'#
function () {}
Emitted when close()
is called.
Also emitted when the input
stream receives its "end" event. The Interface
instance should be considered "finished" once this is emitted. For example, when
the input
stream receives ^D
, respectively known as EOT
.
This event is also called if there is no SIGINT
event listener present when
the input
stream receives a ^C
, respectively known as SIGINT
.
Event: 'SIGINT'#
function () {}
Emitted whenever the input
stream receives a ^C
, respectively known as
SIGINT
. If there is no SIGINT
event listener present when the input
stream receives a SIGINT
, pause
will be triggered.
Example of listening for SIGINT
:
rl.on('SIGINT', function() {
rl.question('Are you sure you want to exit?', function(answer) {
if (answer.match(/^y(es)?$/i)) rl.pause();
});
});
Event: 'SIGTSTP'#
function () {}
This does not work on Windows.
Emitted whenever the input
stream receives a ^Z
, respectively known as
SIGTSTP
. If there is no SIGTSTP
event listener present when the input
stream receives a SIGTSTP
, the program will be sent to the background.
When the program is resumed with fg
, the pause
and SIGCONT
events will be
emitted. You can use either to resume the stream.
The pause
and SIGCONT
events will not be triggered if the stream was paused
before the program was sent to the background.
Example of listening for SIGTSTP
:
rl.on('SIGTSTP', function() {
// This will override SIGTSTP and prevent the program from going to the
// background.
console.log('Caught SIGTSTP.');
});
Event: 'SIGCONT'#
function () {}
This does not work on Windows.
Emitted whenever the input
stream is sent to the background with ^Z
,
respectively known as SIGTSTP
, and then continued with fg(1)
. This event
only emits if the stream was not paused before sending the program to the
background.
Example of listening for SIGCONT
:
rl.on('SIGCONT', function() {
// `prompt` will automatically resume the stream
rl.prompt();
});
Example: Tiny CLI#
Here's an example of how to use all these together to craft a tiny command line interface:
var readline = require('readline'),
rl = readline.createInterface(process.stdin, process.stdout);
rl.setPrompt('OHAI> ');
rl.prompt();
rl.on('line', function(line) {
switch(line.trim()) {
case 'hello':
console.log('world!');
break;
default:
console.log('Say what? I might have heard `' + line.trim() + '`');
break;
}
rl.prompt();
}).on('close', function() {
console.log('Have a great day!');
process.exit(0);
});
readline.cursorTo(stream, x, y)#
Move cursor to the specified position in a given TTY stream.
readline.moveCursor(stream, dx, dy)#
Move cursor relative to it's current position in a given TTY stream.
readline.clearLine(stream, dir)#
Clears current line of given TTY stream in a specified direction.
dir
should have one of following values:
-1
- to the left from cursor1
- to the right from cursor0
- the entire line
readline.clearScreenDown(stream)#
Clears the screen from the current position of the cursor down.
REPL#
Stability: 3 - Stable
A Read-Eval-Print-Loop (REPL) is available both as a standalone program and easily includable in other programs. The REPL provides a way to interactively run JavaScript and see the results. It can be used for debugging, testing, or just trying things out.
By executing node
without any arguments from the command-line you will be
dropped into the REPL. It has simplistic emacs line-editing.
mjr:~$ node
Type '.help' for options.
> a = [ 1, 2, 3];
[ 1, 2, 3 ]
> a.forEach(function (v) {
... console.log(v);
... });
1
2
3
For advanced line-editors, start node with the environmental variable
NODE_NO_READLINE=1
. This will start the main and debugger REPL in canonical
terminal settings which will allow you to use with rlwrap
.
For example, you could add this to your bashrc file:
alias node="env NODE_NO_READLINE=1 rlwrap node"
repl.start(options)#
Returns and starts a REPLServer
instance, that inherits from
[Readline Interface][]. Accepts an "options" Object that takes
the following values:
prompt
- the prompt andstream
for all I/O. Defaults to>
.input
- the readable stream to listen to. Defaults toprocess.stdin
.output
- the writable stream to write readline data to. Defaults toprocess.stdout
.terminal
- passtrue
if thestream
should be treated like a TTY, and have ANSI/VT100 escape codes written to it. Defaults to checkingisTTY
on theoutput
stream upon instantiation.eval
- function that will be used to eval each given line. Defaults to an async wrapper foreval()
. See below for an example of a customeval
.useColors
- a boolean which specifies whether or not thewriter
function should output colors. If a differentwriter
function is set then this does nothing. Defaults to the repl'sterminal
value.useGlobal
- if set totrue
, then the repl will use theglobal
object, instead of running scripts in a separate context. Defaults tofalse
.ignoreUndefined
- if set totrue
, then the repl will not output the return value of command if it'sundefined
. Defaults tofalse
.writer
- the function to invoke for each command that gets evaluated which returns the formatting (including coloring) to display. Defaults toutil.inspect
.
You can use your own eval
function if it has following signature:
function eval(cmd, context, filename, callback) {
callback(null, result);
}
Multiple REPLs may be started against the same running instance of node. Each will share the same global object but will have unique I/O.
Here is an example that starts a REPL on stdin, a Unix socket, and a TCP socket:
var net = require("net"),
repl = require("repl");
connections = 0;
repl.start({
prompt: "node via stdin> ",
input: process.stdin,
output: process.stdout
});
net.createServer(function (socket) {
connections += 1;
repl.start({
prompt: "node via Unix socket> ",
input: socket,
output: socket
}).on('exit', function() {
socket.end();
})
}).listen("/tmp/node-repl-sock");
net.createServer(function (socket) {
connections += 1;
repl.start({
prompt: "node via TCP socket> ",
input: socket,
output: socket
}).on('exit', function() {
socket.end();
});
}).listen(5001);
Running this program from the command line will start a REPL on stdin. Other
REPL clients may connect through the Unix socket or TCP socket. telnet
is useful
for connecting to TCP sockets, and socat
can be used to connect to both Unix and
TCP sockets.
By starting a REPL from a Unix socket-based server instead of stdin, you can connect to a long-running node process without restarting it.
For an example of running a "full-featured" (terminal
) REPL over
a net.Server
and net.Socket
instance, see: https://gist.github.com/2209310
For an example of running a REPL instance over curl(1)
,
see: https://gist.github.com/2053342
Event: 'exit'#
function () {}
Emitted when the user exits the REPL in any of the defined ways. Namely, typing
.exit
at the repl, pressing Ctrl+C twice to signal SIGINT, or pressing Ctrl+D
to signal "end" on the input
stream.
Example of listening for exit
:
r.on('exit', function () {
console.log('Got "exit" event from repl!');
process.exit();
});
Event: 'reset'#
function (context) {}
Emitted when the REPL's context is reset. This happens when you type .clear
.
If you start the repl with { useGlobal: true }
then this event will never
be emitted.
Example of listening for reset
:
// Extend the initial repl context.
r = repl.start({ options ... });
someExtension.extend(r.context);
// When a new context is created extend it as well.
r.on('reset', function (context) {
console.log('repl has a new context');
someExtension.extend(context);
});
REPL Features#
Inside the REPL, Control+D will exit. Multi-line expressions can be input. Tab completion is supported for both global and local variables.
The special variable _
(underscore) contains the result of the last expression.
> [ "a", "b", "c" ]
[ 'a', 'b', 'c' ]
> _.length
3
> _ += 1
4
The REPL provides access to any variables in the global scope. You can expose
a variable to the REPL explicitly by assigning it to the context
object
associated with each REPLServer
. For example:
// repl_test.js
var repl = require("repl"),
msg = "message";
repl.start("> ").context.m = msg;
Things in the context
object appear as local within the REPL:
mjr:~$ node repl_test.js
> m
'message'
There are a few special REPL commands:
.break
- While inputting a multi-line expression, sometimes you get lost or just don't care about completing it..break
will start over..clear
- Resets thecontext
object to an empty object and clears any multi-line expression..exit
- Close the I/O stream, which will cause the REPL to exit..help
- Show this list of special commands..save
- Save the current REPL session to a file.save ./file/to/save.js
.load
- Load a file into the current REPL session..load ./file/to/load.js
The following key combinations in the REPL have these special effects:
<ctrl>C
- Similar to the.break
keyword. Terminates the current command. Press twice on a blank line to forcibly exit.<ctrl>D
- Similar to the.exit
keyword.
Executing JavaScript#
Stability: 3 - Stable
You can access this module with:
var vm = require('vm');
JavaScript code can be compiled and run immediately or compiled, saved, and run later.
vm.runInThisContext(code, [options])#
vm.runInThisContext()
compiles code
, runs it and returns the result. Running
code does not have access to local scope, but does have access to the current
global
object.
Example of using vm.runInThisContext
and eval
to run the same code:
var localVar = 'initial value';
var vmResult = vm.runInThisContext('localVar = "vm";');
console.log('vmResult: ', vmResult);
console.log('localVar: ', localVar);
var evalResult = eval('localVar = "eval";');
console.log('evalResult: ', evalResult);
console.log('localVar: ', localVar);
// vmResult: 'vm', localVar: 'initial value'
// evalResult: 'eval', localVar: 'eval'
vm.runInThisContext
does not have access to the local scope, so localVar
is
unchanged. eval
does have access to the local scope, so localVar
is changed.
In this way vm.runInThisContext
is much like an indirect eval
call,
e.g. (0,eval)('code')
. However, it also has the following additional options:
filename
: allows you to control the filename that shows up in any stack traces produced.displayErrors
: whether or not to print any errors to stderr, with the line of code that caused them highlighted, before throwing an exception. Will capture both syntax errors from compilingcode
and runtime errors thrown by executing the compiled code. Defaults totrue
.timeout
: a number of milliseconds to executecode
before terminating execution. If execution is terminated, anError
will be thrown.
vm.createContext([sandbox])#
If given a sandbox
object, will "contextify" that sandbox so that it can be
used in calls to vm.runInContext
or script.runInContext
. Inside scripts run
as such, sandbox
will be the global object, retaining all its existing
properties but also having the built-in objects and functions any standard
global object has. Outside of scripts run by the vm module, sandbox
will
be unchanged.
If not given a sandbox object, returns a new, empty contextified sandbox object you can use.
This function is useful for creating a sandbox that can be used to run multiple
scripts, e.g. if you were emulating a web browser it could be used to create a
single sandbox representing a window's global object, then run all <script>
tags together inside that sandbox.
vm.isContext(sandbox)#
Returns whether or not a sandbox object has been contextified by calling
vm.createContext
on it.
vm.runInContext(code, contextifiedSandbox, [options])#
vm.runInContext
compiles code
, then runs it in contextifiedSandbox
and
returns the result. Running code does not have access to local scope. The
contextifiedSandbox
object must have been previously contextified via
vm.createContext
; it will be used as the global object for code
.
vm.runInContext
takes the same options as vm.runInThisContext
.
Example: compile and execute different scripts in a single existing context.
var util = require('util');
var vm = require('vm');
var sandbox = { globalVar: 1 };
vm.createContext(sandbox);
for (var i = 0; i < 10; ++i) {
vm.runInContext('globalVar *= 2;', sandbox);
}
console.log(util.inspect(sandbox));
// { globalVar: 1024 }
Note that running untrusted code is a tricky business requiring great care.
vm.runInContext
is quite useful, but safely running untrusted code requires a
separate process.
vm.runInNewContext(code, [sandbox], [options])#
vm.runInNewContext
compiles code
, contextifies sandbox
if passed or
creates a new contextified sandbox if it's omitted, and then runs the code with
the sandbox as the global object and returns the result.
vm.runInNewContext
takes the same options as vm.runInThisContext
.
Example: compile and execute code that increments a global variable and sets a new one. These globals are contained in the sandbox.
var util = require('util');
var vm = require('vm'),
var sandbox = {
animal: 'cat',
count: 2
};
vm.runInNewContext('count += 1; name = "kitty"', sandbox);
console.log(util.inspect(sandbox));
// { animal: 'cat', count: 3, name: 'kitty' }
Note that running untrusted code is a tricky business requiring great care.
vm.runInNewContext
is quite useful, but safely running untrusted code requires
a separate process.
vm.runInDebugContext(code)#
vm.runInDebugContext
compiles and executes code
inside the V8 debug context.
The primary use case is to get access to the V8 debug object:
var Debug = vm.runInDebugContext('Debug');
Debug.scripts().forEach(function(script) { console.log(script.name); });
Note that the debug context and object are intrinsically tied to V8's debugger implementation and may change (or even get removed) without prior warning.
The debug object can also be exposed with the --expose_debug_as=
switch.
Class: Script#
A class for holding precompiled scripts, and running them in specific sandboxes.
new vm.Script(code, options)#
Creating a new Script
compiles code
but does not run it. Instead, the
created vm.Script
object represents this compiled code. This script can be run
later many times using methods below. The returned script is not bound to any
global object. It is bound before each run, just for that run.
The options when creating a script are:
filename
: allows you to control the filename that shows up in any stack traces produced from this script.displayErrors
: whether or not to print any errors to stderr, with the line of code that caused them highlighted, before throwing an exception. Applies only to syntax errors compiling the code; errors while running the code are controlled by the options to the script's methods.
script.runInThisContext([options])#
Similar to vm.runInThisContext
but a method of a precompiled Script
object.
script.runInThisContext
runs script
's compiled code and returns the result.
Running code does not have access to local scope, but does have access to the
current global
object.
Example of using script.runInThisContext
to compile code once and run it
multiple times:
var vm = require('vm');
global.globalVar = 0;
var script = new vm.Script('globalVar += 1', { filename: 'myfile.vm' });
for (var i = 0; i < 1000; ++i) {
script.runInThisContext();
}
console.log(globalVar);
// 1000
The options for running a script are:
displayErrors
: whether or not to print any runtime errors to stderr, with the line of code that caused them highlighted, before throwing an exception. Applies only to runtime errors executing the code; it is impossible to create aScript
instance with syntax errors, as the constructor will throw.timeout
: a number of milliseconds to execute the script before terminating execution. If execution is terminated, anError
will be thrown.
script.runInContext(contextifiedSandbox, [options])#
Similar to vm.runInContext
but a method of a precompiled Script
object.
script.runInContext
runs script
's compiled code in contextifiedSandbox
and returns the result. Running code does not have access to local scope.
script.runInContext
takes the same options as script.runInThisContext
.
Example: compile code that increments a global variable and sets one, then execute the code multiple times. These globals are contained in the sandbox.
var util = require('util');
var vm = require('vm');
var sandbox = {
animal: 'cat',
count: 2
};
var script = new vm.Script('count += 1; name = "kitty"');
for (var i = 0; i < 10; ++i) {
script.runInContext(sandbox);
}
console.log(util.inspect(sandbox));
// { animal: 'cat', count: 12, name: 'kitty' }
Note that running untrusted code is a tricky business requiring great care.
script.runInContext
is quite useful, but safely running untrusted code
requires a separate process.
script.runInNewContext([sandbox], [options])#
Similar to vm.runInNewContext
but a method of a precompiled Script
object.
script.runInNewContext
contextifies sandbox
if passed or creates a new
contextified sandbox if it's omitted, and then runs script
's compiled code
with the sandbox as the global object and returns the result. Running code does
not have access to local scope.
script.runInNewContext
takes the same options as script.runInThisContext
.
Example: compile code that sets a global variable, then execute the code multiple times in different contexts. These globals are set on and contained in the sandboxes.
var util = require('util');
var vm = require('vm');
var sandboxes = [{}, {}, {}];
var script = new vm.Script('globalVar = "set"');
sandboxes.forEach(function (sandbox) {
script.runInNewContext(sandbox);
});
console.log(util.inspect(sandboxes));
// [{ globalVar: 'set' }, { globalVar: 'set' }, { globalVar: 'set' }]
Note that running untrusted code is a tricky business requiring great care.
script.runInNewContext
is quite useful, but safely running untrusted code
requires a separate process.
Child Process#
Stability: 3 - Stable
Node provides a tri-directional popen(3)
facility through the
child_process
module.
It is possible to stream data through a child's stdin
, stdout
, and
stderr
in a fully non-blocking way. (Note that some programs use
line-buffered I/O internally. That doesn't affect node.js but it means
data you send to the child process may not be immediately consumed.)
To create a child process use require('child_process').spawn()
or
require('child_process').fork()
. The semantics of each are slightly
different, and explained below.
For scripting purposes you may find the synchronous counterparts more convenient.
Class: ChildProcess#
ChildProcess
is an EventEmitter.
Child processes always have three streams associated with them. child.stdin
,
child.stdout
, and child.stderr
. These may be shared with the stdio
streams of the parent process, or they may be separate stream objects
which can be piped to and from.
The ChildProcess class is not intended to be used directly. Use the
spawn()
, exec()
, execFile()
, or fork()
methods to create a Child
Process instance.
Event: 'error'#
err
Error Object the error.
Emitted when:
- The process could not be spawned, or
- The process could not be killed, or
- Sending a message to the child process failed for whatever reason.
Note that the exit
-event may or may not fire after an error has occurred. If
you are listening on both events to fire a function, remember to guard against
calling your function twice.
See also ChildProcess#kill()
and
ChildProcess#send()
.
Event: 'exit'#
code
Number the exit code, if it exited normally.signal
String the signal passed to kill the child process, if it was killed by the parent.
This event is emitted after the child process ends. If the process terminated
normally, code
is the final exit code of the process, otherwise null
. If
the process terminated due to receipt of a signal, signal
is the string name
of the signal, otherwise null
.
Note that the child process stdio streams might still be open.
Also, note that node establishes signal handlers for 'SIGINT'
and 'SIGTERM
',
so it will not terminate due to receipt of those signals, it will exit.
See waitpid(2)
.
Event: 'close'#
code
Number the exit code, if it exited normally.signal
String the signal passed to kill the child process, if it was killed by the parent.
This event is emitted when the stdio streams of a child process have all terminated. This is distinct from 'exit', since multiple processes might share the same stdio streams.
Event: 'disconnect'#
This event is emitted after calling the .disconnect()
method in the parent
or in the child. After disconnecting it is no longer possible to send messages,
and the .connected
property is false.
Event: 'message'#
message
Object a parsed JSON object or primitive valuesendHandle
Handle object a Socket or Server object
Messages send by .send(message, [sendHandle])
are obtained using the
message
event.
child.stdin#
- Stream object
A Writable Stream
that represents the child process's stdin
.
Closing this stream via end()
often causes the child process to terminate.
If the child stdio streams are shared with the parent, then this will not be set.
child.stdout#
- Stream object
A Readable Stream
that represents the child process's stdout
.
If the child stdio streams are shared with the parent, then this will not be set.
child.stderr#
- Stream object
A Readable Stream
that represents the child process's stderr
.
If the child stdio streams are shared with the parent, then this will not be set.
child.pid#
- Integer
The PID of the child process.
Example:
var spawn = require('child_process').spawn,
grep = spawn('grep', ['ssh']);
console.log('Spawned child pid: ' + grep.pid);
grep.stdin.end();
child.connected#
- Boolean Set to false after `.disconnect' is called
If .connected
is false, it is no longer possible to send messages.
child.kill([signal])#
signal
String
Send a signal to the child process. If no argument is given, the process will
be sent 'SIGTERM'
. See signal(7)
for a list of available signals.
var spawn = require('child_process').spawn,
grep = spawn('grep', ['ssh']);
grep.on('close', function (code, signal) {
console.log('child process terminated due to receipt of signal '+signal);
});
// send SIGHUP to process
grep.kill('SIGHUP');
May emit an 'error'
event when the signal cannot be delivered. Sending a
signal to a child process that has already exited is not an error but may
have unforeseen consequences: if the PID (the process ID) has been reassigned
to another process, the signal will be delivered to that process instead.
What happens next is anyone's guess.
Note that while the function is called kill
, the signal delivered to the
child process may not actually kill it. kill
really just sends a signal
to a process.
See kill(2)
child.send(message, [sendHandle])#
message
ObjectsendHandle
Handle object
When using child_process.fork()
you can write to the child using
child.send(message, [sendHandle])
and messages are received by
a 'message'
event on the child.
For example:
var cp = require('child_process');
var n = cp.fork(__dirname + '/sub.js');
n.on('message', function(m) {
console.log('PARENT got message:', m);
});
n.send({ hello: 'world' });
And then the child script, 'sub.js'
might look like this:
process.on('message', function(m) {
console.log('CHILD got message:', m);
});
process.send({ foo: 'bar' });
In the child the process
object will have a send()
method, and process
will emit objects each time it receives a message on its channel.
Please note that the send()
method on both the parent and child are
synchronous - sending large chunks of data is not advised (pipes can be used
instead, see
child_process.spawn
).
There is a special case when sending a {cmd: 'NODE_foo'}
message. All messages
containing a NODE_
prefix in its cmd
property will not be emitted in
the message
event, since they are internal messages used by node core.
Messages containing the prefix are emitted in the internalMessage
event, you
should by all means avoid using this feature, it is subject to change without notice.
The sendHandle
option to child.send()
is for sending a TCP server or
socket object to another process. The child will receive the object as its
second argument to the message
event.
Emits an 'error'
event if the message cannot be sent, for example because
the child process has already exited.
Example: sending server object#
Here is an example of sending a server:
var child = require('child_process').fork('child.js');
// Open up the server object and send the handle.
var server = require('net').createServer();
server.on('connection', function (socket) {
socket.end('handled by parent');
});
server.listen(1337, function() {
child.send('server', server);
});
And the child would the receive the server object as:
process.on('message', function(m, server) {
if (m === 'server') {
server.on('connection', function (socket) {
socket.end('handled by child');
});
}
});
Note that the server is now shared between the parent and child, this means that some connections will be handled by the parent and some by the child.
For dgram
servers the workflow is exactly the same. Here you listen on
a message
event instead of connection
and use server.bind
instead of
server.listen
. (Currently only supported on UNIX platforms.)
Example: sending socket object#
Here is an example of sending a socket. It will spawn two children and handle
connections with the remote address 74.125.127.100
as VIP by sending the
socket to a "special" child process. Other sockets will go to a "normal" process.
var normal = require('child_process').fork('child.js', ['normal']);
var special = require('child_process').fork('child.js', ['special']);
// Open up the server and send sockets to child
var server = require('net').createServer();
server.on('connection', function (socket) {
// if this is a VIP
if (socket.remoteAddress === '74.125.127.100') {
special.send('socket', socket);
return;
}
// just the usual dudes
normal.send('socket', socket);
});
server.listen(1337);
The child.js
could look like this:
process.on('message', function(m, socket) {
if (m === 'socket') {
socket.end('You were handled as a ' + process.argv[2] + ' person');
}
});
Note that once a single socket has been sent to a child the parent can no
longer keep track of when the socket is destroyed. To indicate this condition
the .connections
property becomes null
.
It is also recommended not to use .maxConnections
in this condition.
child.disconnect()#
Close the IPC channel between parent and child, allowing the child to exit
gracefully once there are no other connections keeping it alive. After calling
this method the .connected
flag will be set to false
in both the parent and
child, and it is no longer possible to send messages.
The 'disconnect' event will be emitted when there are no messages in the process of being received, most likely immediately.
Note that you can also call process.disconnect()
in the child process when the
child process has any open IPC channels with the parent (i.e fork()
).
Asynchronous Process Creation#
These methods follow the common async programming patterns (accepting a callback or returning an EventEmitter).
child_process.spawn(command, [args], [options])#
command
String The command to runargs
Array List of string argumentsoptions
Objectcwd
String Current working directory of the child processstdio
Array|String Child's stdio configuration. (See below)env
Object Environment key-value pairsdetached
Boolean The child will be a process group leader. (See below)uid
Number Sets the user identity of the process. (See setuid(2).)gid
Number Sets the group identity of the process. (See setgid(2).)
- return: ChildProcess object
Launches a new process with the given command
, with command line arguments in args
.
If omitted, args
defaults to an empty Array.
The third argument is used to specify additional options, with these defaults:
{ cwd: undefined,
env: process.env
}
cwd
allows you to specify the working directory from which the process is spawned.
Use env
to specify environment variables that will be visible to the new process.
Example of running ls -lh /usr
, capturing stdout
, stderr
, and the exit code:
var spawn = require('child_process').spawn,
ls = spawn('ls', ['-lh', '/usr']);
ls.stdout.on('data', function (data) {
console.log('stdout: ' + data);
});
ls.stderr.on('data', function (data) {
console.log('stderr: ' + data);
});
ls.on('close', function (code) {
console.log('child process exited with code ' + code);
});
Example: A very elaborate way to run 'ps ax | grep ssh'
var spawn = require('child_process').spawn,
ps = spawn('ps', ['ax']),
grep = spawn('grep', ['ssh']);
ps.stdout.on('data', function (data) {
grep.stdin.write(data);
});
ps.stderr.on('data', function (data) {
console.log('ps stderr: ' + data);
});
ps.on('close', function (code) {
if (code !== 0) {
console.log('ps process exited with code ' + code);
}
grep.stdin.end();
});
grep.stdout.on('data', function (data) {
console.log('' + data);
});
grep.stderr.on('data', function (data) {
console.log('grep stderr: ' + data);
});
grep.on('close', function (code) {
if (code !== 0) {
console.log('grep process exited with code ' + code);
}
});
Example of checking for failed exec:
var spawn = require('child_process').spawn,
child = spawn('bad_command');
child.on('error', function (err) {
console.log('Failed to start child process.');
});
The 'stdio' option to child_process.spawn()
is an array where each
index corresponds to a fd in the child. The value is one of the following:
'pipe'
- Create a pipe between the child process and the parent process. The parent end of the pipe is exposed to the parent as a property on thechild_process
object asChildProcess.stdio[fd]
. Pipes created for fds 0 - 2 are also available as ChildProcess.stdin, ChildProcess.stdout and ChildProcess.stderr, respectively.'ipc'
- Create an IPC channel for passing messages/file descriptors between parent and child. A ChildProcess may have at most one IPC stdio file descriptor. Setting this option enables the ChildProcess.send() method. If the child writes JSON messages to this file descriptor, then this will trigger ChildProcess.on('message'). If the child is a Node.js program, then the presence of an IPC channel will enable process.send() and process.on('message').'ignore'
- Do not set this file descriptor in the child. Note that Node will always open fd 0 - 2 for the processes it spawns. When any of these is ignored node will open/dev/null
and attach it to the child's fd.Stream
object - Share a readable or writable stream that refers to a tty, file, socket, or a pipe with the child process. The stream's underlying file descriptor is duplicated in the child process to the fd that corresponds to the index in thestdio
array. Note that the stream must have an underlying descriptor (file streams do not until the'open'
event has occurred).- Positive integer - The integer value is interpreted as a file descriptor
that is is currently open in the parent process. It is shared with the child
process, similar to how
Stream
objects can be shared. null
,undefined
- Use default value. For stdio fds 0, 1 and 2 (in other words, stdin, stdout, and stderr) a pipe is created. For fd 3 and up, the default is'ignore'
.
As a shorthand, the stdio
argument may also be one of the following
strings, rather than an array:
ignore
-['ignore', 'ignore', 'ignore']
pipe
-['pipe', 'pipe', 'pipe']
inherit
-[process.stdin, process.stdout, process.stderr]
or[0,1,2]
Example:
var spawn = require('child_process').spawn;
// Child will use parent's stdios
spawn('prg', [], { stdio: 'inherit' });
// Spawn child sharing only stderr
spawn('prg', [], { stdio: ['pipe', 'pipe', process.stderr] });
// Open an extra fd=4, to interact with programs present a
// startd-style interface.
spawn('prg', [], { stdio: ['pipe', null, null, null, 'pipe'] });
If the detached
option is set, the child process will be made the leader of a
new process group. This makes it possible for the child to continue running
after the parent exits.
By default, the parent will wait for the detached child to exit. To prevent
the parent from waiting for a given child
, use the child.unref()
method,
and the parent's event loop will not include the child in its reference count.
Example of detaching a long-running process and redirecting its output to a file:
var fs = require('fs'),
spawn = require('child_process').spawn,
out = fs.openSync('./out.log', 'a'),
err = fs.openSync('./out.log', 'a');
var child = spawn('prg', [], {
detached: true,
stdio: [ 'ignore', out, err ]
});
child.unref();
When using the detached
option to start a long-running process, the process
will not stay running in the background unless it is provided with a stdio
configuration that is not connected to the parent. If the parent's stdio
is
inherited, the child will remain attached to the controlling terminal.
See also: child_process.exec()
and child_process.fork()
child_process.exec(command, [options], callback)#
command
String The command to run, with space-separated argumentsoptions
Objectcwd
String Current working directory of the child processenv
Object Environment key-value pairsencoding
String (Default: 'utf8')shell
String Shell to execute the command with (Default: '/bin/sh' on UNIX, 'cmd.exe' on Windows, The shell should understand the-c
switch on UNIX or/s /c
on Windows. On Windows, command line parsing should be compatible withcmd.exe
.)timeout
Number (Default: 0)maxBuffer
Number (Default:200*1024
)killSignal
String (Default: 'SIGTERM')uid
Number Sets the user identity of the process. (See setuid(2).)gid
Number Sets the group identity of the process. (See setgid(2).)
callback
Function called with the output when process terminateserror
Errorstdout
Bufferstderr
Buffer
- Return: ChildProcess object
Runs a command in a shell and buffers the output.
var exec = require('child_process').exec,
child;
child = exec('cat *.js bad_file | wc -l',
function (error, stdout, stderr) {
console.log('stdout: ' + stdout);
console.log('stderr: ' + stderr);
if (error !== null) {
console.log('exec error: ' + error);
}
});
The callback gets the arguments (error, stdout, stderr)
. On success, error
will be null
. On error, error
will be an instance of Error
and error.code
will be the exit code of the child process, and error.signal
will be set to the
signal that terminated the process.
There is a second optional argument to specify several options. The default options are
{ encoding: 'utf8',
timeout: 0,
maxBuffer: 200*1024,
killSignal: 'SIGTERM',
cwd: null,
env: null }
If timeout
is greater than 0, then it will kill the child process
if it runs longer than timeout
milliseconds. The child process is killed with
killSignal
(default: 'SIGTERM'
). maxBuffer
specifies the largest
amount of data allowed on stdout or stderr - if this value is exceeded then
the child process is killed.
child_process.execFile(file, [args], [options], [callback])#
file
String The filename of the program to runargs
Array List of string argumentsoptions
Objectcwd
String Current working directory of the child processenv
Object Environment key-value pairsencoding
String (Default: 'utf8')timeout
Number (Default: 0)maxBuffer
Number (Default: 200*1024)killSignal
String (Default: 'SIGTERM')uid
Number Sets the user identity of the process. (See setuid(2).)gid
Number Sets the group identity of the process. (See setgid(2).)
callback
Function called with the output when process terminateserror
Errorstdout
Bufferstderr
Buffer
- Return: ChildProcess object
This is similar to child_process.exec()
except it does not execute a
subshell but rather the specified file directly. This makes it slightly
leaner than child_process.exec
. It has the same options.
child_process.fork(modulePath, [args], [options])#
modulePath
String The module to run in the childargs
Array List of string argumentsoptions
Objectcwd
String Current working directory of the child processenv
Object Environment key-value pairsencoding
String (Default: 'utf8')execPath
String Executable used to create the child processexecArgv
Array List of string arguments passed to the executable (Default:process.execArgv
)silent
Boolean If true, stdin, stdout, and stderr of the child will be piped to the parent, otherwise they will be inherited from the parent, see the "pipe" and "inherit" options forspawn()
'sstdio
for more details (default is false)uid
Number Sets the user identity of the process. (See setuid(2).)gid
Number Sets the group identity of the process. (See setgid(2).)
- Return: ChildProcess object
This is a special case of the spawn()
functionality for spawning Node
processes. In addition to having all the methods in a normal ChildProcess
instance, the returned object has a communication channel built-in. See
child.send(message, [sendHandle])
for details.
These child Nodes are still whole new instances of V8. Assume at least 30ms startup and 10mb memory for each new Node. That is, you cannot create many thousands of them.
The execPath
property in the options
object allows for a process to be
created for the child rather than the current node
executable. This should be
done with care and by default will talk over the fd represented an
environmental variable NODE_CHANNEL_FD
on the child process. The input and
output on this fd is expected to be line delimited JSON objects.
Synchronous Process Creation#
These methods are synchronous, meaning they WILL block the event loop, pausing execution of your code until the spawned process exits.
Blocking calls like these are mostly useful for simplifying general purpose scripting tasks and for simplifying the loading/processing of application configuration at startup.
child_process.spawnSync(command, [args], [options])#
command
String The command to runargs
Array List of string argumentsoptions
Objectcwd
String Current working directory of the child processinput
String|Buffer The value which will be passed as stdin to the spawned process- supplying this value will override
stdio[0]
- supplying this value will override
stdio
Array Child's stdio configuration.env
Object Environment key-value pairsuid
Number Sets the user identity of the process. (See setuid(2).)gid
Number Sets the group identity of the process. (See setgid(2).)timeout
Number In milliseconds the maximum amount of time the process is allowed to run. (Default: undefined)killSignal
String The signal value to be used when the spawned process will be killed. (Default: 'SIGTERM')maxBuffer
Numberencoding
String The encoding used for all stdio inputs and outputs. (Default: 'buffer')
- return: Object
pid
Number Pid of the child processoutput
Array Array of results from stdio outputstdout
Buffer|String The contents ofoutput[1]
stderr
Buffer|String The contents ofoutput[2]
status
Number The exit code of the child processsignal
String The signal used to kill the child processerror
Error The error object if the child process failed or timed out
spawnSync
will not return until the child process has fully closed. When a
timeout has been encountered and killSignal
is sent, the method won't return
until the process has completely exited. That is to say, if the process handles
the SIGTERM
signal and doesn't exit, your process will wait until the child
process has exited.
child_process.execFileSync(command, [args], [options])#
command
String The command to runargs
Array List of string argumentsoptions
Objectcwd
String Current working directory of the child processinput
String|Buffer The value which will be passed as stdin to the spawned process- supplying this value will override
stdio[0]
- supplying this value will override
stdio
Array Child's stdio configuration. (Default: 'pipe')stderr
by default will be output to the parent process' stderr unlessstdio
is specified
env
Object Environment key-value pairsuid
Number Sets the user identity of the process. (See setuid(2).)gid
Number Sets the group identity of the process. (See setgid(2).)timeout
Number In milliseconds the maximum amount of time the process is allowed to run. (Default: undefined)killSignal
String The signal value to be used when the spawned process will be killed. (Default: 'SIGTERM')maxBuffer
Numberencoding
String The encoding used for all stdio inputs and outputs. (Default: 'buffer')
- return: Buffer|String The stdout from the command
execFileSync
will not return until the child process has fully closed. When a
timeout has been encountered and killSignal
is sent, the method won't return
until the process has completely exited. That is to say, if the process handles
the SIGTERM
signal and doesn't exit, your process will wait until the child
process has exited.
If the process times out, or has a non-zero exit code, this method will
throw. The Error
object will contain the entire result from
child_process.spawnSync
child_process.execSync(command, [options])#
command
String The command to runoptions
Objectcwd
String Current working directory of the child processinput
String|Buffer The value which will be passed as stdin to the spawned process- supplying this value will override
stdio[0]
- supplying this value will override
stdio
Array Child's stdio configuration. (Default: 'pipe')stderr
by default will be output to the parent process' stderr unlessstdio
is specified
env
Object Environment key-value pairsuid
Number Sets the user identity of the process. (See setuid(2).)gid
Number Sets the group identity of the process. (See setgid(2).)timeout
Number In milliseconds the maximum amount of time the process is allowed to run. (Default: undefined)killSignal
String The signal value to be used when the spawned process will be killed. (Default: 'SIGTERM')maxBuffer
Numberencoding
String The encoding used for all stdio inputs and outputs. (Default: 'buffer')
- return: Buffer|String The stdout from the command
execSync
will not return until the child process has fully closed. When a
timeout has been encountered and killSignal
is sent, the method won't return
until the process has completely exited. That is to say, if the process handles
the SIGTERM
signal and doesn't exit, your process will wait until the child
process has exited.
If the process times out, or has a non-zero exit code, this method will
throw. The Error
object will contain the entire result from
child_process.spawnSync
Assert#
Stability: 5 - Locked
This module is used for writing unit tests for your applications, you can
access it with require('assert')
.
assert.fail(actual, expected, message, operator)#
Throws an exception that displays the values for actual
and expected
separated by the provided operator.
assert(value, message), assert.ok(value, [message])#
Tests if value is truthy, it is equivalent to assert.equal(true, !!value, message);
assert.equal(actual, expected, [message])#
Tests shallow, coercive equality with the equal comparison operator ( ==
).
assert.notEqual(actual, expected, [message])#
Tests shallow, coercive non-equality with the not equal comparison operator ( !=
).
assert.deepEqual(actual, expected, [message])#
Tests for deep equality.
assert.notDeepEqual(actual, expected, [message])#
Tests for any deep inequality.
assert.strictEqual(actual, expected, [message])#
Tests strict equality, as determined by the strict equality operator ( ===
)
assert.notStrictEqual(actual, expected, [message])#
Tests strict non-equality, as determined by the strict not equal operator ( !==
)
assert.throws(block, [error], [message])#
Expects block
to throw an error. error
can be constructor, RegExp
or
validation function.
Validate instanceof using constructor:
assert.throws(
function() {
throw new Error("Wrong value");
},
Error
);
Validate error message using RegExp:
assert.throws(
function() {
throw new Error("Wrong value");
},
/value/
);
Custom error validation:
assert.throws(
function() {
throw new Error("Wrong value");
},
function(err) {
if ( (err instanceof Error) && /value/.test(err) ) {
return true;
}
},
"unexpected error"
);
assert.doesNotThrow(block, [message])#
Expects block
not to throw an error, see assert.throws
for details.
assert.ifError(value)#
Tests if value is not a false value, throws if it is a true value. Useful when
testing the first argument, error
in callbacks.
TTY#
Stability: 2 - Unstable
The tty
module houses the tty.ReadStream
and tty.WriteStream
classes. In
most cases, you will not need to use this module directly.
When node detects that it is being run inside a TTY context, then process.stdin
will be a tty.ReadStream
instance and process.stdout
will be
a tty.WriteStream
instance. The preferred way to check if node is being run in
a TTY context is to check process.stdout.isTTY
:
$ node -p -e "Boolean(process.stdout.isTTY)"
true
$ node -p -e "Boolean(process.stdout.isTTY)" | cat
false
tty.isatty(fd)#
Returns true
or false
depending on if the fd
is associated with a
terminal.
tty.setRawMode(mode)#
Deprecated. Use tty.ReadStream#setRawMode()
(i.e. process.stdin.setRawMode()
) instead.
Class: ReadStream#
A net.Socket
subclass that represents the readable portion of a tty. In normal
circumstances, process.stdin
will be the only tty.ReadStream
instance in any
node program (only when isatty(0)
is true).
rs.isRaw#
A Boolean
that is initialized to false
. It represents the current "raw" state
of the tty.ReadStream
instance.
rs.setRawMode(mode)#
mode
should be true
or false
. This sets the properties of the
tty.ReadStream
to act either as a raw device or default. isRaw
will be set
to the resulting mode.
Class: WriteStream#
A net.Socket
subclass that represents the writable portion of a tty. In normal
circumstances, process.stdout
will be the only tty.WriteStream
instance
ever created (and only when isatty(1)
is true).
ws.columns#
A Number
that gives the number of columns the TTY currently has. This property
gets updated on "resize" events.
ws.rows#
A Number
that gives the number of rows the TTY currently has. This property
gets updated on "resize" events.
Event: 'resize'#
function () {}
Emitted by refreshSize()
when either of the columns
or rows
properties
has changed.
process.stdout.on('resize', function() {
console.log('screen size has changed!');
console.log(process.stdout.columns + 'x' + process.stdout.rows);
});
Zlib#
Stability: 3 - Stable
You can access this module with:
var zlib = require('zlib');
This provides bindings to Gzip/Gunzip, Deflate/Inflate, and DeflateRaw/InflateRaw classes. Each class takes the same options, and is a readable/writable Stream.
Examples#
Compressing or decompressing a file can be done by piping an fs.ReadStream into a zlib stream, then into an fs.WriteStream.
var gzip = zlib.createGzip();
var fs = require('fs');
var inp = fs.createReadStream('input.txt');
var out = fs.createWriteStream('input.txt.gz');
inp.pipe(gzip).pipe(out);
Compressing or decompressing data in one step can be done by using the convenience methods.
var input = '.................................';
zlib.deflate(input, function(err, buffer) {
if (!err) {
console.log(buffer.toString('base64'));
}
});
var buffer = new Buffer('eJzT0yMAAGTvBe8=', 'base64');
zlib.unzip(buffer, function(err, buffer) {
if (!err) {
console.log(buffer.toString());
}
});
To use this module in an HTTP client or server, use the accept-encoding on requests, and the content-encoding header on responses.
Note: these examples are drastically simplified to show the basic concept. Zlib encoding can be expensive, and the results ought to be cached. See Memory Usage Tuning below for more information on the speed/memory/compression tradeoffs involved in zlib usage.
// client request example
var zlib = require('zlib');
var http = require('http');
var fs = require('fs');
var request = http.get({ host: 'izs.me',
path: '/',
port: 80,
headers: { 'accept-encoding': 'gzip,deflate' } });
request.on('response', function(response) {
var output = fs.createWriteStream('izs.me_index.html');
switch (response.headers['content-encoding']) {
// or, just use zlib.createUnzip() to handle both cases
case 'gzip':
response.pipe(zlib.createGunzip()).pipe(output);
break;
case 'deflate':
response.pipe(zlib.createInflate()).pipe(output);
break;
default:
response.pipe(output);
break;
}
});
// server example
// Running a gzip operation on every request is quite expensive.
// It would be much more efficient to cache the compressed buffer.
var zlib = require('zlib');
var http = require('http');
var fs = require('fs');
http.createServer(function(request, response) {
var raw = fs.createReadStream('index.html');
var acceptEncoding = request.headers['accept-encoding'];
if (!acceptEncoding) {
acceptEncoding = '';
}
// Note: this is not a conformant accept-encoding parser.
// See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.3
if (acceptEncoding.match(/\bdeflate\b/)) {
response.writeHead(200, { 'content-encoding': 'deflate' });
raw.pipe(zlib.createDeflate()).pipe(response);
} else if (acceptEncoding.match(/\bgzip\b/)) {
response.writeHead(200, { 'content-encoding': 'gzip' });
raw.pipe(zlib.createGzip()).pipe(response);
} else {
response.writeHead(200, {});
raw.pipe(response);
}
}).listen(1337);
zlib.createGzip([options])#
Returns a new Gzip object with an options.
zlib.createGunzip([options])#
Returns a new Gunzip object with an options.
zlib.createDeflate([options])#
Returns a new Deflate object with an options.
zlib.createInflate([options])#
Returns a new Inflate object with an options.
zlib.createDeflateRaw([options])#
Returns a new DeflateRaw object with an options.
zlib.createInflateRaw([options])#
Returns a new InflateRaw object with an options.
zlib.createUnzip([options])#
Returns a new Unzip object with an options.
Class: zlib.Zlib#
Not exported by the zlib
module. It is documented here because it is the base
class of the compressor/decompressor classes.
zlib.flush([kind], callback)#
kind
defaults to zlib.Z_FULL_FLUSH
.
Flush pending data. Don't call this frivolously, premature flushes negatively impact the effectiveness of the compression algorithm.
zlib.params(level, strategy, callback)#
Dynamically update the compression level and compression strategy. Only applicable to deflate algorithm.
zlib.reset()#
Reset the compressor/decompressor to factory defaults. Only applicable to the inflate and deflate algorithms.
Class: zlib.Gzip#
Compress data using gzip.
Class: zlib.Gunzip#
Decompress a gzip stream.
Class: zlib.Deflate#
Compress data using deflate.
Class: zlib.Inflate#
Decompress a deflate stream.
Class: zlib.DeflateRaw#
Compress data using deflate, and do not append a zlib header.
Class: zlib.InflateRaw#
Decompress a raw deflate stream.
Class: zlib.Unzip#
Decompress either a Gzip- or Deflate-compressed stream by auto-detecting the header.
Convenience Methods#
All of these take a string or buffer as the first argument, an optional second
argument to supply options to the zlib classes and will call the supplied
callback with callback(error, result)
.
Every method has a *Sync
counterpart, which accept the same arguments, but
without a callback.
zlib.deflate(buf, [options], callback)#
zlib.deflateSync(buf, [options])#
Compress a string with Deflate.
zlib.deflateRaw(buf, [options], callback)#
zlib.deflateRawSync(buf, [options])#
Compress a string with DeflateRaw.
zlib.gzip(buf, [options], callback)#
zlib.gzipSync(buf, [options])#
Compress a string with Gzip.
zlib.gunzip(buf, [options], callback)#
zlib.gunzipSync(buf, [options])#
Decompress a raw Buffer with Gunzip.
zlib.inflate(buf, [options], callback)#
zlib.inflateSync(buf, [options])#
Decompress a raw Buffer with Inflate.
zlib.inflateRaw(buf, [options], callback)#
zlib.inflateRawSync(buf, [options])#
Decompress a raw Buffer with InflateRaw.
zlib.unzip(buf, [options], callback)#
zlib.unzipSync(buf, [options])#
Decompress a raw Buffer with Unzip.
Options#
Each class takes an options object. All options are optional.
Note that some options are only relevant when compressing, and are ignored by the decompression classes.
- flush (default:
zlib.Z_NO_FLUSH
) - chunkSize (default: 16*1024)
- windowBits
- level (compression only)
- memLevel (compression only)
- strategy (compression only)
- dictionary (deflate/inflate only, empty dictionary by default)
See the description of deflateInit2
and inflateInit2
at
http://zlib.net/manual.html#Advanced for more information on these.
Memory Usage Tuning#
From zlib/zconf.h
, modified to node's usage:
The memory requirements for deflate are (in bytes):
(1 << (windowBits+2)) + (1 << (memLevel+9))
that is: 128K for windowBits=15 + 128K for memLevel = 8 (default values) plus a few kilobytes for small objects.
For example, if you want to reduce the default memory requirements from 256K to 128K, set the options to:
{ windowBits: 14, memLevel: 7 }
Of course this will generally degrade compression (there's no free lunch).
The memory requirements for inflate are (in bytes)
1 << windowBits
that is, 32K for windowBits=15 (default value) plus a few kilobytes for small objects.
This is in addition to a single internal output slab buffer of size
chunkSize
, which defaults to 16K.
The speed of zlib compression is affected most dramatically by the
level
setting. A higher level will result in better compression, but
will take longer to complete. A lower level will result in less
compression, but will be much faster.
In general, greater memory usage options will mean that node has to make
fewer calls to zlib, since it'll be able to process more data in a
single write
operation. So, this is another factor that affects the
speed, at the cost of memory usage.
Constants#
All of the constants defined in zlib.h are also defined on
require('zlib')
.
In the normal course of operations, you will not need to ever set any of
these. They are documented here so that their presence is not
surprising. This section is taken almost directly from the zlib
documentation. See
http://zlib.net/manual.html#Constants for more details.
Allowed flush values.
zlib.Z_NO_FLUSH
zlib.Z_PARTIAL_FLUSH
zlib.Z_SYNC_FLUSH
zlib.Z_FULL_FLUSH
zlib.Z_FINISH
zlib.Z_BLOCK
zlib.Z_TREES
Return codes for the compression/decompression functions. Negative values are errors, positive values are used for special but normal events.
zlib.Z_OK
zlib.Z_STREAM_END
zlib.Z_NEED_DICT
zlib.Z_ERRNO
zlib.Z_STREAM_ERROR
zlib.Z_DATA_ERROR
zlib.Z_MEM_ERROR
zlib.Z_BUF_ERROR
zlib.Z_VERSION_ERROR
Compression levels.
zlib.Z_NO_COMPRESSION
zlib.Z_BEST_SPEED
zlib.Z_BEST_COMPRESSION
zlib.Z_DEFAULT_COMPRESSION
Compression strategy.
zlib.Z_FILTERED
zlib.Z_HUFFMAN_ONLY
zlib.Z_RLE
zlib.Z_FIXED
zlib.Z_DEFAULT_STRATEGY
Possible values of the data_type field.
zlib.Z_BINARY
zlib.Z_TEXT
zlib.Z_ASCII
zlib.Z_UNKNOWN
The deflate compression method (the only one supported in this version).
zlib.Z_DEFLATED
For initializing zalloc, zfree, opaque.
zlib.Z_NULL
os#
Stability: 4 - API Frozen
Provides a few basic operating-system related utility functions.
Use require('os')
to access this module.
os.tmpdir()#
Returns the operating system's default directory for temp files.
os.endianness()#
Returns the endianness of the CPU. Possible values are "BE"
or "LE"
.
os.hostname()#
Returns the hostname of the operating system.
os.type()#
Returns the operating system name.
os.platform()#
Returns the operating system platform.
os.arch()#
Returns the operating system CPU architecture. Possible values are "x64"
,
"arm"
and "ia32"
.
os.release()#
Returns the operating system release.
os.uptime()#
Returns the system uptime in seconds.
os.loadavg()#
Returns an array containing the 1, 5, and 15 minute load averages.
The load average is a measure of system activity, calculated by the operating system and expressed as a fractional number. As a rule of thumb, the load average should ideally be less than the number of logical CPUs in the system.
The load average is a very UNIX-y concept; there is no real equivalent on
Windows platforms. That is why this function always returns [0, 0, 0]
on
Windows.
os.totalmem()#
Returns the total amount of system memory in bytes.
os.freemem()#
Returns the amount of free system memory in bytes.
os.cpus()#
Returns an array of objects containing information about each CPU/core installed: model, speed (in MHz), and times (an object containing the number of milliseconds the CPU/core spent in: user, nice, sys, idle, and irq).
Example inspection of os.cpus:
[ { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',
speed: 2926,
times:
{ user: 252020,
nice: 0,
sys: 30340,
idle: 1070356870,
irq: 0 } },
{ model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',
speed: 2926,
times:
{ user: 306960,
nice: 0,
sys: 26980,
idle: 1071569080,
irq: 0 } },
{ model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',
speed: 2926,
times:
{ user: 248450,
nice: 0,
sys: 21750,
idle: 1070919370,
irq: 0 } },
{ model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',
speed: 2926,
times:
{ user: 256880,
nice: 0,
sys: 19430,
idle: 1070905480,
irq: 20 } },
{ model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',
speed: 2926,
times:
{ user: 511580,
nice: 20,
sys: 40900,
idle: 1070842510,
irq: 0 } },
{ model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',
speed: 2926,
times:
{ user: 291660,
nice: 0,
sys: 34360,
idle: 1070888000,
irq: 10 } },
{ model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',
speed: 2926,
times:
{ user: 308260,
nice: 0,
sys: 55410,
idle: 1071129970,
irq: 880 } },
{ model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',
speed: 2926,
times:
{ user: 266450,
nice: 1480,
sys: 34920,
idle: 1072572010,
irq: 30 } } ]
os.networkInterfaces()#
Get a list of network interfaces:
{ lo:
[ { address: '127.0.0.1',
netmask: '255.0.0.0',
family: 'IPv4',
mac: '00:00:00:00:00:00',
internal: true },
{ address: '::1',
netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',
family: 'IPv6',
mac: '00:00:00:00:00:00',
internal: true } ],
eth0:
[ { address: '192.168.1.108',
netmask: '255.255.255.0',
family: 'IPv4',
mac: '01:02:03:0a:0b:0c',
internal: false },
{ address: 'fe80::a00:27ff:fe4e:66a1',
netmask: 'ffff:ffff:ffff:ffff::',
family: 'IPv6',
mac: '01:02:03:0a:0b:0c',
internal: false } ] }
os.EOL#
A constant defining the appropriate End-of-line marker for the operating system.
Debugger#
Stability: 3 - Stable
V8 comes with an extensive debugger which is accessible out-of-process via a
simple TCP protocol.
Node has a built-in client for this debugger. To use this, start Node with the
debug
argument; a prompt will appear:
% node debug myscript.js
< debugger listening on port 5858
connecting... ok
break in /home/indutny/Code/git/indutny/myscript.js:1
1 x = 5;
2 setTimeout(function () {
3 debugger;
debug>
Node's debugger client doesn't support the full range of commands, but
simple step and inspection is possible. By putting the statement debugger;
into the source code of your script, you will enable a breakpoint.
For example, suppose myscript.js
looked like this:
// myscript.js
x = 5;
setTimeout(function () {
debugger;
console.log("world");
}, 1000);
console.log("hello");
Then once the debugger is run, it will break on line 4.
% node debug myscript.js
< debugger listening on port 5858
connecting... ok
break in /home/indutny/Code/git/indutny/myscript.js:1
1 x = 5;
2 setTimeout(function () {
3 debugger;
debug> cont
< hello
break in /home/indutny/Code/git/indutny/myscript.js:3
1 x = 5;
2 setTimeout(function () {
3 debugger;
4 console.log("world");
5 }, 1000);
debug> next
break in /home/indutny/Code/git/indutny/myscript.js:4
2 setTimeout(function () {
3 debugger;
4 console.log("world");
5 }, 1000);
6 console.log("hello");
debug> repl
Press Ctrl + C to leave debug repl
> x
5
> 2+2
4
debug> next
< world
break in /home/indutny/Code/git/indutny/myscript.js:5
3 debugger;
4 console.log("world");
5 }, 1000);
6 console.log("hello");
7
debug> quit
%
The repl
command allows you to evaluate code remotely. The next
command
steps over to the next line. There are a few other commands available and more
to come. Type help
to see others.
Watchers#
You can watch expression and variable values while debugging your code. On every breakpoint each expression from the watchers list will be evaluated in the current context and displayed just before the breakpoint's source code listing.
To start watching an expression, type watch("my_expression")
. watchers
prints the active watchers. To remove a watcher, type
unwatch("my_expression")
.
Commands reference#
Stepping#
cont
,c
- Continue executionnext
,n
- Step nextstep
,s
- Step inout
,o
- Step outpause
- Pause running code (like pause button in Developer Tools)
Breakpoints#
setBreakpoint()
,sb()
- Set breakpoint on current linesetBreakpoint(line)
,sb(line)
- Set breakpoint on specific linesetBreakpoint('fn()')
,sb(...)
- Set breakpoint on a first statement in functions bodysetBreakpoint('script.js', 1)
,sb(...)
- Set breakpoint on first line of script.jsclearBreakpoint
,cb(...)
- Clear breakpoint
It is also possible to set a breakpoint in a file (module) that isn't loaded yet:
% ./node debug test/fixtures/break-in-module/main.js
< debugger listening on port 5858
connecting to port 5858... ok
break in test/fixtures/break-in-module/main.js:1
1 var mod = require('./mod.js');
2 mod.hello();
3 mod.hello();
debug> setBreakpoint('mod.js', 23)
Warning: script 'mod.js' was not loaded yet.
1 var mod = require('./mod.js');
2 mod.hello();
3 mod.hello();
debug> c
break in test/fixtures/break-in-module/mod.js:23
21
22 exports.hello = function() {
23 return 'hello from module';
24 };
25
debug>
Info#
backtrace
,bt
- Print backtrace of current execution framelist(5)
- List scripts source code with 5 line context (5 lines before and after)watch(expr)
- Add expression to watch listunwatch(expr)
- Remove expression from watch listwatchers
- List all watchers and their values (automatically listed on each breakpoint)repl
- Open debugger's repl for evaluation in debugging script's context
Execution control#
run
- Run script (automatically runs on debugger's start)restart
- Restart scriptkill
- Kill script
Various#
scripts
- List all loaded scriptsversion
- Display v8's version
Advanced Usage#
The V8 debugger can be enabled and accessed either by starting Node with
the --debug
command-line flag or by signaling an existing Node process
with SIGUSR1
.
Once a process has been set in debug mode with this it can be connected to
with the node debugger. Either connect to the pid
or the URI to the debugger.
The syntax is:
node debug -p <pid>
- Connects to the process via thepid
node debug <URI>
- Connects to the process via the URI such as localhost:5858
Cluster#
Stability: 2 - Unstable
A single instance of Node runs in a single thread. To take advantage of multi-core systems the user will sometimes want to launch a cluster of Node processes to handle the load.
The cluster module allows you to easily create child processes that all share server ports.
var cluster = require('cluster');
var http = require('http');
var numCPUs = require('os').cpus().length;
if (cluster.isMaster) {
// Fork workers.
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
cluster.on('exit', function(worker, code, signal) {
console.log('worker ' + worker.process.pid + ' died');
});
} else {
// Workers can share any TCP connection
// In this case its a HTTP server
http.createServer(function(req, res) {
res.writeHead(200);
res.end("hello world\n");
}).listen(8000);
}
Running node will now share port 8000 between the workers:
% NODE_DEBUG=cluster node server.js
23521,Master Worker 23524 online
23521,Master Worker 23526 online
23521,Master Worker 23523 online
23521,Master Worker 23528 online
This feature was introduced recently, and may change in future versions. Please try it out and provide feedback.
Also note that, on Windows, it is not yet possible to set up a named pipe server in a worker.
How It Works#
The worker processes are spawned using the child_process.fork
method,
so that they can communicate with the parent via IPC and pass server
handles back and forth.
The cluster module supports two methods of distributing incoming connections.
The first one (and the default one on all platforms except Windows), is the round-robin approach, where the master process listens on a port, accepts new connections and distributes them across the workers in a round-robin fashion, with some built-in smarts to avoid overloading a worker process.
The second approach is where the master process creates the listen socket and sends it to interested workers. The workers then accept incoming connections directly.
The second approach should, in theory, give the best performance. In practice however, distribution tends to be very unbalanced due to operating system scheduler vagaries. Loads have been observed where over 70% of all connections ended up in just two processes, out of a total of eight.
Because server.listen()
hands off most of the work to the master
process, there are three cases where the behavior between a normal
node.js process and a cluster worker differs:
server.listen({fd: 7})
Because the message is passed to the master, file descriptor 7 in the parent will be listened on, and the handle passed to the worker, rather than listening to the worker's idea of what the number 7 file descriptor references.server.listen(handle)
Listening on handles explicitly will cause the worker to use the supplied handle, rather than talk to the master process. If the worker already has the handle, then it's presumed that you know what you are doing.server.listen(0)
Normally, this will cause servers to listen on a random port. However, in a cluster, each worker will receive the same "random" port each time they dolisten(0)
. In essence, the port is random the first time, but predictable thereafter. If you want to listen on a unique port, generate a port number based on the cluster worker ID.
There is no routing logic in Node.js, or in your program, and no shared state between the workers. Therefore, it is important to design your program such that it does not rely too heavily on in-memory data objects for things like sessions and login.
Because workers are all separate processes, they can be killed or re-spawned depending on your program's needs, without affecting other workers. As long as there are some workers still alive, the server will continue to accept connections. Node does not automatically manage the number of workers for you, however. It is your responsibility to manage the worker pool for your application's needs.
cluster.schedulingPolicy#
The scheduling policy, either cluster.SCHED_RR
for round-robin or
cluster.SCHED_NONE
to leave it to the operating system. This is a
global setting and effectively frozen once you spawn the first worker
or call cluster.setupMaster()
, whatever comes first.
SCHED_RR
is the default on all operating systems except Windows.
Windows will change to SCHED_RR
once libuv is able to effectively
distribute IOCP handles without incurring a large performance hit.
cluster.schedulingPolicy
can also be set through the
NODE_CLUSTER_SCHED_POLICY
environment variable. Valid
values are "rr"
and "none"
.
cluster.settings#
- Object
execArgv
Array list of string arguments passed to the node executable. (Default=process.execArgv
)exec
String file path to worker file. (Default=process.argv[1]
)args
Array string arguments passed to worker. (Default=process.argv.slice(2)
)silent
Boolean whether or not to send output to parent's stdio. (Default=false
)uid
Number Sets the user identity of the process. (See setuid(2).)gid
Number Sets the group identity of the process. (See setgid(2).)
After calling .setupMaster()
(or .fork()
) this settings object will contain
the settings, including the default values.
It is effectively frozen after being set, because .setupMaster()
can
only be called once.
This object is not supposed to be changed or set manually, by you.
cluster.isMaster#
- Boolean
True if the process is a master. This is determined
by the process.env.NODE_UNIQUE_ID
. If process.env.NODE_UNIQUE_ID
is
undefined, then isMaster
is true
.
cluster.isWorker#
- Boolean
True if the process is not a master (it is the negation of cluster.isMaster
).
Event: 'fork'#
worker
Worker object
When a new worker is forked the cluster module will emit a 'fork' event. This can be used to log worker activity, and create your own timeout.
var timeouts = [];
function errorMsg() {
console.error("Something must be wrong with the connection ...");
}
cluster.on('fork', function(worker) {
timeouts[worker.id] = setTimeout(errorMsg, 2000);
});
cluster.on('listening', function(worker, address) {
clearTimeout(timeouts[worker.id]);
});
cluster.on('exit', function(worker, code, signal) {
clearTimeout(timeouts[worker.id]);
errorMsg();
});
Event: 'online'#
worker
Worker object
After forking a new worker, the worker should respond with an online message. When the master receives an online message it will emit this event. The difference between 'fork' and 'online' is that fork is emitted when the master forks a worker, and 'online' is emitted when the worker is running.
cluster.on('online', function(worker) {
console.log("Yay, the worker responded after it was forked");
});
Event: 'listening'#
worker
Worker objectaddress
Object
After calling listen()
from a worker, when the 'listening' event is emitted on
the server, a listening event will also be emitted on cluster
in the master.
The event handler is executed with two arguments, the worker
contains the worker
object and the address
object contains the following connection properties:
address
, port
and addressType
. This is very useful if the worker is listening
on more than one address.
cluster.on('listening', function(worker, address) {
console.log("A worker is now connected to " + address.address + ":" + address.port);
});
The addressType
is one of:
4
(TCPv4)6
(TCPv6)-1
(unix domain socket)"udp4"
or"udp6"
(UDP v4 or v6)
Event: 'disconnect'#
worker
Worker object
Emitted after the worker IPC channel has disconnected. This can occur when a worker exits gracefully, is killed, or is disconnected manually (such as with worker.disconnect()).
There may be a delay between the disconnect
and exit
events. These events
can be used to detect if the process is stuck in a cleanup or if there are
long-living connections.
cluster.on('disconnect', function(worker) {
console.log('The worker #' + worker.id + ' has disconnected');
});
Event: 'exit'#
worker
Worker objectcode
Number the exit code, if it exited normally.signal
String the name of the signal (eg.'SIGHUP'
) that caused the process to be killed.
When any of the workers die the cluster module will emit the 'exit' event.
This can be used to restart the worker by calling .fork()
again.
cluster.on('exit', function(worker, code, signal) {
console.log('worker %d died (%s). restarting...',
worker.process.pid, signal || code);
cluster.fork();
});
See child_process event: 'exit'.
Event: 'setup'#
settings
Object
Emitted every time .setupMaster()
is called.
The settings
object is the cluster.settings
object at the time
.setupMaster()
was called and is advisory only, since multiple calls to
.setupMaster()
can be made in a single tick.
If accuracy is important, use cluster.settings
.
cluster.setupMaster([settings])#
settings
Objectexec
String file path to worker file. (Default=process.argv[1]
)args
Array string arguments passed to worker. (Default=process.argv.slice(2)
)silent
Boolean whether or not to send output to parent's stdio. (Default=false
)
setupMaster
is used to change the default 'fork' behavior. Once called,
the settings will be present in cluster.settings
.
Note that:
- any settings changes only affect future calls to
.fork()
and have no effect on workers that are already running - The only attribute of a worker that cannot be set via
.setupMaster()
is theenv
passed to.fork()
- the defaults above apply to the first call only, the defaults for later
calls is the current value at the time of
cluster.setupMaster()
is called
Example:
var cluster = require('cluster');
cluster.setupMaster({
exec: 'worker.js',
args: ['--use', 'https'],
silent: true
});
cluster.fork(); // https worker
cluster.setupMaster({
args: ['--use', 'http']
});
cluster.fork(); // http worker
This can only be called from the master process.
cluster.fork([env])#
env
Object Key/value pairs to add to worker process environment.- return Worker object
Spawn a new worker process.
This can only be called from the master process.
cluster.disconnect([callback])#
callback
Function called when all workers are disconnected and handles are closed
Calls .disconnect()
on each worker in cluster.workers
.
When they are disconnected all internal handles will be closed, allowing the master process to die gracefully if no other event is waiting.
The method takes an optional callback argument which will be called when finished.
This can only be called from the master process.
cluster.worker#
- Object
A reference to the current worker object. Not available in the master process.
var cluster = require('cluster');
if (cluster.isMaster) {
console.log('I am master');
cluster.fork();
cluster.fork();
} else if (cluster.isWorker) {
console.log('I am worker #' + cluster.worker.id);
}
cluster.workers#
- Object
A hash that stores the active worker objects, keyed by id
field. Makes it
easy to loop through all the workers. It is only available in the master
process.
A worker is removed from cluster.workers after the worker has disconnected and
exited. The order between these two events cannot be determined in advance.
However, it is guaranteed that the removal from the cluster.workers list happens
before last 'disconnect'
or 'exit'
event is emitted.
// Go through all workers
function eachWorker(callback) {
for (var id in cluster.workers) {
callback(cluster.workers[id]);
}
}
eachWorker(function(worker) {
worker.send('big announcement to all workers');
});
Should you wish to reference a worker over a communication channel, using the worker's unique id is the easiest way to find the worker.
socket.on('data', function(id) {
var worker = cluster.workers[id];
});
Class: Worker#
A Worker object contains all public information and method about a worker.
In the master it can be obtained using cluster.workers
. In a worker
it can be obtained using cluster.worker
.
worker.id#
- String
Each new worker is given its own unique id, this id is stored in the
id
.
While a worker is alive, this is the key that indexes it in cluster.workers
worker.process#
- ChildProcess object
All workers are created using child_process.fork()
, the returned object
from this function is stored as .process
. In a worker, the global process
is stored.
See: Child Process module
Note that workers will call process.exit(0)
if the 'disconnect'
event occurs
on process
and .suicide
is not true
. This protects against accidental
disconnection.
worker.suicide#
- Boolean
Set by calling .kill()
or .disconnect()
, until then it is undefined
.
The boolean worker.suicide
lets you distinguish between voluntary and accidental
exit, the master may choose not to respawn a worker based on this value.
cluster.on('exit', function(worker, code, signal) {
if (worker.suicide === true) {
console.log('Oh, it was just suicide\' – no need to worry').
}
});
// kill worker
worker.kill();
worker.send(message, [sendHandle])#
message
ObjectsendHandle
Handle object
This function is equal to the send methods provided by
child_process.fork()
. In the master you should use this function to
send a message to a specific worker.
In a worker you can also use process.send(message)
, it is the same function.
This example will echo back all messages from the master:
if (cluster.isMaster) {
var worker = cluster.fork();
worker.send('hi there');
} else if (cluster.isWorker) {
process.on('message', function(msg) {
process.send(msg);
});
}
worker.kill([signal='SIGTERM'])#
signal
String Name of the kill signal to send to the worker process.
This function will kill the worker. In the master, it does this by disconnecting
the worker.process
, and once disconnected, killing with signal
. In the
worker, it does it by disconnecting the channel, and then exiting with code 0
.
Causes .suicide
to be set.
This method is aliased as worker.destroy()
for backwards compatibility.
Note that in a worker, process.kill()
exists, but it is not this function,
it is kill.
worker.disconnect()#
In a worker, this function will close all servers, wait for the 'close' event on those servers, and then disconnect the IPC channel.
In the master, an internal message is sent to the worker causing it to call
.disconnect()
on itself.
Causes .suicide
to be set.
Note that after a server is closed, it will no longer accept new connections, but connections may be accepted by any other listening worker. Existing connections will be allowed to close as usual. When no more connections exist, see server.close(), the IPC channel to the worker will close allowing it to die gracefully.
The above applies only to server connections, client connections are not automatically closed by workers, and disconnect does not wait for them to close before exiting.
Note that in a worker, process.disconnect
exists, but it is not this function,
it is disconnect.
Because long living server connections may block workers from disconnecting, it
may be useful to send a message, so application specific actions may be taken to
close them. It also may be useful to implement a timeout, killing a worker if
the disconnect
event has not been emitted after some time.
if (cluster.isMaster) {
var worker = cluster.fork();
var timeout;
worker.on('listening', function(address) {
worker.send('shutdown');
worker.disconnect();
timeout = setTimeout(function() {
worker.kill();
}, 2000);
});
worker.on('disconnect', function() {
clearTimeout(timeout);
});
} else if (cluster.isWorker) {
var net = require('net');
var server = net.createServer(function(socket) {
// connections never end
});
server.listen(8000);
process.on('message', function(msg) {
if(msg === 'shutdown') {
// initiate graceful close of any connections to server
}
});
}
worker.isDead()#
This function returns true
if the worker's process has terminated (either
because of exiting or being signaled). Otherwise, it returns false
.
worker.isConnected()#
This function returns true
if the worker is connected to its master via its IPC
channel, false
otherwise. A worker is connected to its master after it's been
created. It is disconnected after the disconnect
event is emitted.
Event: 'message'#
message
Object
This event is the same as the one provided by child_process.fork()
.
In a worker you can also use process.on('message')
.
As an example, here is a cluster that keeps count of the number of requests in the master process using the message system:
var cluster = require('cluster');
var http = require('http');
if (cluster.isMaster) {
// Keep track of http requests
var numReqs = 0;
setInterval(function() {
console.log("numReqs =", numReqs);
}, 1000);
// Count requestes
function messageHandler(msg) {
if (msg.cmd && msg.cmd == 'notifyRequest') {
numReqs += 1;
}
}
// Start workers and listen for messages containing notifyRequest
var numCPUs = require('os').cpus().length;
for (var i = 0; i < numCPUs; i++) {
cluster.fork();
}
Object.keys(cluster.workers).forEach(function(id) {
cluster.workers[id].on('message', messageHandler);
});
} else {
// Worker processes have a http server.
http.Server(function(req, res) {
res.writeHead(200);
res.end("hello world\n");
// notify master about the request
process.send({ cmd: 'notifyRequest' });
}).listen(8000);
}
Event: 'online'#
Similar to the cluster.on('online')
event, but specific to this worker.
cluster.fork().on('online', function() {
// Worker is online
});
It is not emitted in the worker.
Event: 'listening'#
address
Object
Similar to the cluster.on('listening')
event, but specific to this worker.
cluster.fork().on('listening', function(address) {
// Worker is listening
});
It is not emitted in the worker.
Event: 'disconnect'#
Similar to the cluster.on('disconnect')
event, but specfic to this worker.
cluster.fork().on('disconnect', function() {
// Worker has disconnected
});
Event: 'exit'#
code
Number the exit code, if it exited normally.signal
String the name of the signal (eg.'SIGHUP'
) that caused the process to be killed.
Similar to the cluster.on('exit')
event, but specific to this worker.
var worker = cluster.fork();
worker.on('exit', function(code, signal) {
if( signal ) {
console.log("worker was killed by signal: "+signal);
} else if( code !== 0 ) {
console.log("worker exited with error code: "+code);
} else {
console.log("worker success!");
}
});
Event: 'error'#
This event is the same as the one provided by child_process.fork()
.
In a worker you can also use process.on('error')
.
Smalloc#
Stability: 1 - Experimental
smalloc.alloc(length[, receiver][, type])#
length
{Number}<= smalloc.kMaxLength
receiver
{Object}, Optional, Default:new Object
type
{Enum}, Optional, Default:Uint8
Returns receiver
with allocated external array data. If no receiver
is
passed then a new Object will be created and returned.
Buffers are backed by a simple allocator that only handles the assignation of external raw memory. Smalloc exposes that functionality.
This can be used to create your own Buffer-like classes. No other properties are
set, so the user will need to keep track of other necessary information (e.g.
length
of the allocation).
function SimpleData(n) {
this.length = n;
smalloc.alloc(this.length, this);
}
SimpleData.prototype = { /* ... */ };
It only checks if the receiver
is an Object, and also not an Array. Because of
this it is possible to allocate external array data to more than a plain Object.
function allocMe() { }
smalloc.alloc(3, allocMe);
// { [Function allocMe] '0': 0, '1': 0, '2': 0 }
v8 does not support allocating external array data to an Array, and if passed will throw.
It's possible is to specify the type of external array data you would like. All
possible options are listed in smalloc.Types
. Example usage:
var doubleArr = smalloc.alloc(3, smalloc.Types.Double);
for (var i = 0; i < 3; i++)
doubleArr = i / 10;
// { '0': 0, '1': 0.1, '2': 0.2 }
smalloc.copyOnto(source, sourceStart, dest, destStart, copyLength);#
source
Object with external array allocationsourceStart
Position to begin copying fromdest
Object with external array allocationdestStart
Position to begin copying ontocopyLength
Length of copy
Copy memory from one external array allocation to another. No arguments are optional, and any violation will throw.
var a = smalloc.alloc(4);
var b = smalloc.alloc(4);
for (var i = 0; i < 4; i++) {
a[i] = i;
b[i] = i * 2;
}
// { '0': 0, '1': 1, '2': 2, '3': 3 }
// { '0': 0, '1': 2, '2': 4, '3': 6 }
smalloc.copyOnto(b, 2, a, 0, 2);
// { '0': 4, '1': 6, '2': 2, '3': 3 }
copyOnto
automatically detects the length of the allocation internally, so no
need to set any additional properties for this to work.
smalloc.dispose(obj)#
obj
Object
Free memory that has been allocated to an object via smalloc.alloc
.
var a = {};
smalloc.alloc(3, a);
// { '0': 0, '1': 0, '2': 0 }
smalloc.dispose(a);
// {}
This is useful to reduce strain on the garbage collector, but developers must be careful. Cryptic errors may arise in applications that are difficult to trace.
var a = smalloc.alloc(4);
var b = smalloc.alloc(4);
// perform this somewhere along the line
smalloc.dispose(b);
// now trying to copy some data out
smalloc.copyOnto(b, 2, a, 0, 2);
// now results in:
// Error: source has no external array data
dispose()
does not support Buffers, and will throw if passed.
smalloc.hasExternalData(obj)#
obj
Object
Returns true
if the obj
has externally allocated memory.
smalloc.kMaxLength#
Size of maximum allocation. This is also applicable to Buffer creation.
smalloc.Types#
Enum of possible external array types. Contains:
Int8
Uint8
Int16
Uint16
Int32
Uint32
Float
Double
Uint8Clamped
Tracing#
Stability: 1 - Experimental
The tracing module is designed for instrumenting your Node application. It is not meant for general purpose use.
Be very careful with callbacks used in conjunction with this module
Many of these callbacks interact directly with asynchronous subsystems in a
synchronous fashion. That is to say, you may be in a callback where a call to
console.log()
could result in an infinite recursive loop. Also of note, many
of these callbacks are in hot execution code paths. That is to say your
callbacks are executed quite often in the normal operation of Node, so be wary
of doing CPU bound or synchronous workloads in these functions. Consider a ring
buffer and a timer to defer processing.
require('tracing')
to use this module.
v8#
The v8
property is an EventEmitter, it exposes events and interfaces
specific to the version of v8
built with node. These interfaces are subject
to change by upstream and are therefore not covered under the stability index.
Event: 'gc'#
function (before, after) { }
Emitted each time a GC run is completed.
before
and after
are objects with the following properties:
{
type: 'mark-sweep-compact',
flags: 0,
timestamp: 905535650119053,
total_heap_size: 6295040,
total_heap_size_executable: 4194304,
total_physical_size: 6295040,
used_heap_size: 2855416,
heap_size_limit: 1535115264
}
getHeapStatistics()#
Returns an object with the following properties
{
total_heap_size: 7326976,
total_heap_size_executable: 4194304,
total_physical_size: 7326976,
used_heap_size: 3476208,
heap_size_limit: 1535115264
}
Async Listeners#
The AsyncListener
API is the JavaScript interface for the AsyncWrap
class which allows developers to be notified about key events in the
lifetime of an asynchronous event. Node performs a lot of asynchronous
events internally, and significant use of this API may have a
significant performance impact on your application.
tracing.createAsyncListener(callbacksObj[, userData])#
callbacksObj
Object Contains optional callbacks that will fire at specific times in the life cycle of the asynchronous event.userData
Value a value that will be passed to all callbacks.
Returns a constructed AsyncListener
object.
To begin capturing asynchronous events pass either the callbacksObj
or
pass an existing AsyncListener
instance to tracing.addAsyncListener()
.
The same AsyncListener
instance can only be added once to the active
queue, and subsequent attempts to add the instance will be ignored.
To stop capturing pass the AsyncListener
instance to
tracing.removeAsyncListener()
. This does not mean the
AsyncListener
previously added will stop triggering callbacks. Once
attached to an asynchronous event it will persist with the lifetime of the
asynchronous call stack.
Explanation of function parameters:
callbacksObj
: An Object
which may contain several optional fields:
create(userData)
: AFunction
called when an asynchronous event is instantiated. If aValue
is returned then it will be attached to the event and overwrite any value that had been passed totracing.createAsyncListener()
'suserData
argument. If an initialuserData
was passed when created, thencreate()
will receive that as a function argument.before(context, userData)
: AFunction
that is called immediately before the asynchronous callback is about to run. It will be passed both thecontext
(i.e.this
) of the calling function and theuserData
either returned fromcreate()
or passed during construction (if either occurred).after(context, userData)
: AFunction
called immediately after the asynchronous event's callback has run. Note this will not be called if the callback throws and the error is not handled.error(userData, error)
: AFunction
called if the event's callback threw. If this registered callback returnstrue
then Node will assume the error has been properly handled and resume execution normally. When multipleerror()
callbacks have been registered only one of those callbacks needs to returntrue
forAsyncListener
to accept that the error has been handled, but allerror()
callbacks will always be run.
userData
: A Value
(i.e. anything) that will be, by default,
attached to all new event instances. This will be overwritten if a Value
is returned by create()
.
Here is an example of overwriting the userData
:
tracing.createAsyncListener({
create: function listener(value) {
// value === true
return false;
}, {
before: function before(context, value) {
// value === false
}
}, true);
Note: The EventEmitter, while used to emit status of an asynchronous
event, is not itself asynchronous. So create()
will not fire when
an event is added, and before()
/after()
will not fire when emitted
callbacks are called.
tracing.addAsyncListener(callbacksObj[, userData])#
tracing.addAsyncListener(asyncListener)#
Returns a constructed AsyncListener
object and immediately adds it to
the listening queue to begin capturing asynchronous events.
Function parameters can either be the same as
tracing.createAsyncListener()
, or a constructed AsyncListener
object.
Example usage for capturing errors:
var fs = require('fs');
var cntr = 0;
var key = tracing.addAsyncListener({
create: function onCreate() {
return { uid: cntr++ };
},
before: function onBefore(context, storage) {
// Write directly to stdout or we'll enter a recursive loop
fs.writeSync(1, 'uid: ' + storage.uid + ' is about to run\n');
},
after: function onAfter(context, storage) {
fs.writeSync(1, 'uid: ' + storage.uid + ' ran\n');
},
error: function onError(storage, err) {
// Handle known errors
if (err.message === 'everything is fine') {
// Writing to stderr this time.
fs.writeSync(2, 'handled error just threw:\n');
fs.writeSync(2, err.stack + '\n');
return true;
}
}
});
process.nextTick(function() {
throw new Error('everything is fine');
});
// Output:
// uid: 0 is about to run
// handled error just threw:
// Error: really, it's ok
// at /tmp/test2.js:27:9
// at process._tickCallback (node.js:583:11)
// at Function.Module.runMain (module.js:492:11)
// at startup (node.js:123:16)
// at node.js:1012:3
tracing.removeAsyncListener(asyncListener)#
Removes the AsyncListener
from the listening queue.
Removing the AsyncListener
from the active queue does not mean the
asyncListener
callbacks will cease to fire on the events they've been
registered. Subsequently, any asynchronous events fired during the
execution of a callback will also have the same asyncListener
callbacks
attached for future execution. For example:
var fs = require('fs');
var key = tracing.createAsyncListener({
create: function asyncListener() {
// Write directly to stdout or we'll enter a recursive loop
fs.writeSync(1, 'You summoned me?\n');
}
});
// We want to begin capturing async events some time in the future.
setTimeout(function() {
tracing.addAsyncListener(key);
// Perform a few additional async events.
setTimeout(function() {
setImmediate(function() {
process.nextTick(function() { });
});
});
// Removing the listener doesn't mean to stop capturing events that
// have already been added.
tracing.removeAsyncListener(key);
}, 100);
// Output:
// You summoned me?
// You summoned me?
// You summoned me?
// You summoned me?
The fact that we logged 4 asynchronous events is an implementation detail of Node's Timers.
To stop capturing from a specific asynchronous event stack
tracing.removeAsyncListener()
must be called from within the call
stack itself. For example:
var fs = require('fs');
var key = tracing.createAsyncListener({
create: function asyncListener() {
// Write directly to stdout or we'll enter a recursive loop
fs.writeSync(1, 'You summoned me?\n');
}
});
// We want to begin capturing async events some time in the future.
setTimeout(function() {
tracing.addAsyncListener(key);
// Perform a few additional async events.
setImmediate(function() {
// Stop capturing from this call stack.
tracing.removeAsyncListener(key);
process.nextTick(function() { });
});
}, 100);
// Output:
// You summoned me?
The user must be explicit and always pass the AsyncListener
they wish
to remove. It is not possible to simply remove all listeners at once.