{ "type": "module", "source": "doc/api/environment_variables.md", "modules": [ { "textRaw": "Environment Variables", "name": "environment_variables", "introduced_in": "v20.12.0", "desc": "

Environment variables are variables associated to the environment the Node.js process runs in.

", "modules": [ { "textRaw": "CLI Environment Variables", "name": "cli_environment_variables", "desc": "

There is a set of environment variables that can be defined to customize the behavior of Node.js,\nfor more details refer to the CLI Environment Variables documentation.

", "type": "module", "displayName": "CLI Environment Variables" }, { "textRaw": "DotEnv", "name": "dotenv", "desc": "

Set of utilities for dealing with additional environment variables defined in .env files.

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\n

Stability: 2 - Stable

\n
", "modules": [ { "textRaw": ".env files", "name": ".env_files", "desc": "

.env files (also known as dotenv files) are files that define environment variables,\nwhich Node.js applications can then interact with (popularized by the dotenv package).

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The following is an example of the content of a basic .env file:

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MY_VAR_A = \"my variable A\"\nMY_VAR_B = \"my variable B\"\n
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This type of file is used in various different programming languages and platforms but there\nis no formal specification for it, therefore Node.js defines its own specification described below.

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A .env file is a file that contains key-value pairs, each pair is represented by a variable name\nfollowed by the equal sign (=) followed by a variable value.

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The name of such files is usually .env or it starts with .env (like for example .env.dev where\ndev indicates a specific target environment). This is the recommended naming scheme but it is not\nmandatory and dotenv files can have any arbitrary file name.

", "modules": [ { "textRaw": "Variable Names", "name": "variable_names", "desc": "

A valid variable name must contain only letters (uppercase or lowercase), digits and underscores\n(_) and it can't begin with a digit.

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More specifically a valid variable name must match the following regular expression:

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^[a-zA-Z_]+[a-zA-Z0-9_]*$\n
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The recommended convention is to use capital letters with underscores and digits when necessary,\nbut any variable name respecting the above definition will work just fine.

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For example, the following are some valid variable names: MY_VAR, MY_VAR_1, my_var, my_var_1,\nmyVar, My_Var123, while these are instead not valid: 1_VAR, 'my-var', \"my var\", VAR_#1.

", "type": "module", "displayName": "Variable Names" }, { "textRaw": "Variable Values", "name": "variable_values", "desc": "

Variable values are comprised by any arbitrary text, which can optionally be wrapped inside\nsingle (') or double (\") quotes.

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Quoted variables can span across multiple lines, while non quoted ones are restricted to a single line.

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Noting that when parsed by Node.js all values are interpreted as text, meaning that any value will\nresult in a JavaScript string inside Node.js. For example the following values: 0, true and\n{ \"hello\": \"world\" } will result in the literal strings '0', 'true' and '{ \"hello\": \"world\" }'\ninstead of the number zero, the boolean true and an object with the hello property respectively.

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Examples of valid variables:

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MY_SIMPLE_VAR = a simple single line variable\nMY_EQUALS_VAR = \"this variable contains an = sign!\"\nMY_HASH_VAR = 'this variable contains a # symbol!'\nMY_MULTILINE_VAR = '\nthis is a multiline variable containing\ntwo separate lines\\nSorry, I meant three lines'\n
", "type": "module", "displayName": "Variable Values" }, { "textRaw": "Spacing", "name": "spacing", "desc": "

Leading and trailing whitespace characters around variable keys and values are ignored unless they\nare enclosed within quotes.

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For example:

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   MY_VAR_A   =    my variable a\n    MY_VAR_B   =    '   my variable b   '\n
\n

will be treated identically to:

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MY_VAR_A = my variable a\nMY_VAR_B = '   my variable b   '\n
", "type": "module", "displayName": "Spacing" }, { "textRaw": "Comments", "name": "comments", "desc": "

Hash-tag (#) characters denote the beginning of a comment, meaning that the rest of the line\nwill be completely ignored.

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Hash-tags found within quotes are however treated as any other standard character.

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For example:

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# This is a comment\nMY_VAR = my variable # This is also a comment\nMY_VAR_A = \"# this is NOT a comment\"\n
", "type": "module", "displayName": "Comments" }, { "textRaw": "`export` prefixes", "name": "`export`_prefixes", "desc": "

The export keyword can optionally be added in front of variable declarations, such keyword will be completely ignored\nby all processing done on the file.

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This is useful so that the file can be sourced, without modifications, in shell terminals.

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Example:

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export MY_VAR = my variable\n
", "type": "module", "displayName": "`export` prefixes" } ], "type": "module", "displayName": ".env files" }, { "textRaw": "CLI Options", "name": "cli_options", "desc": "

.env files can be used to populate the process.env object via one the following CLI options:

\n", "type": "module", "displayName": "CLI Options" }, { "textRaw": "Programmatic APIs", "name": "programmatic_apis", "desc": "

There following two functions allow you to directly interact with .env files:

\n", "type": "module", "displayName": "Programmatic APIs" } ], "type": "module", "displayName": "DotEnv" } ], "properties": [ { "textRaw": "`process.env`", "name": "env", "desc": "

The basic API for interacting with environment variables is process.env, it consists of an object\nwith pre-populated user environment variables that can be modified and expanded.

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For more details refer to the process.env documentation.

" } ], "type": "module", "displayName": "Environment Variables" } ] }