Command Line Interface

To run ESLint on Node.js, you must have npm installed. If npm is not installed, follow the instructions here: https://www.npmjs.com/

Once npm is installed, run the following

npm i -g eslint

This installs the ESLint CLI from the npm repository. To run ESLint, use the following format:

eslint [options] [file|dir|glob]*

Such as:

eslint file1.js file2.js

or:

eslint lib/**

Please note that when passing a glob as a parameter, it will be expanded by your shell. The results of the expansion can vary depending on your shell, and its configuration. If you want to use node glob syntax, you have to quote your parameter (using double quotes if you need it to run in Windows), as follows:

eslint "lib/**"

Options

The command line utility has several options. You can view the options by running eslint -h.

eslint [options] file.js [file.js] [dir]

Basic configuration:
  --no-eslintrc                  Disable use of configuration from .eslintrc.*
  -c, --config path::String      Use this configuration, overriding .eslintrc.* config options if present
  --env [String]                 Specify environments
  --ext [String]                 Specify JavaScript file extensions - default: .js
  --global [String]              Define global variables
  --parser String                Specify the parser to be used
  --parser-options Object        Specify parser options
  --resolve-plugins-relative-to path::String  A folder where plugins should be resolved from, CWD by default

Specifying rules and plugins:
  --rulesdir [path::String]      Use additional rules from this directory
  --plugin [String]              Specify plugins
  --rule Object                  Specify rules

Fixing problems:
  --fix                          Automatically fix problems
  --fix-dry-run                  Automatically fix problems without saving the changes to the file system
  --fix-type Array               Specify the types of fixes to apply (directive, problem, suggestion, layout)

Ignoring files:
  --ignore-path path::String     Specify path of ignore file
  --no-ignore                    Disable use of ignore files and patterns
  --ignore-pattern [String]      Pattern of files to ignore (in addition to those in .eslintignore)

Using stdin:
  --stdin                        Lint code provided on <STDIN> - default: false
  --stdin-filename String        Specify filename to process STDIN as

Handling warnings:
  --quiet                        Report errors only - default: false
  --max-warnings Int             Number of warnings to trigger nonzero exit code - default: -1

Output:
  -o, --output-file path::String  Specify file to write report to
  -f, --format String            Use a specific output format - default: stylish
  --color, --no-color            Force enabling/disabling of color

Inline configuration comments:
  --no-inline-config             Prevent comments from changing config or rules
  --report-unused-disable-directives  Adds reported errors for unused eslint-disable directives

Caching:
  --cache                        Only check changed files - default: false
  --cache-file path::String      Path to the cache file. Deprecated: use --cache-location - default: .eslintcache
  --cache-location path::String  Path to the cache file or directory
  --cache-strategy String        Strategy to use for detecting changed files - either: metadata or content - default: metadata

Miscellaneous:
  --init                         Run config initialization wizard - default: false
  --env-info                     Output execution environment information - default: false
  --no-error-on-unmatched-pattern  Prevent errors when pattern is unmatched - default: false
  --exit-on-fatal-error          Exit with exit code 2 in case of fatal error - default: false
  --debug                        Output debugging information
  -h, --help                     Show help
  -v, --version                  Output the version number
  --print-config path::String    Print the configuration for the given file

Options that accept array values can be specified by repeating the option or with a comma-delimited list (other than --ignore-pattern which does not allow the second style).

Example:

eslint --ext .jsx --ext .js lib/

eslint --ext .jsx,.js lib/

Basic configuration

--no-eslintrc

Disables use of configuration from .eslintrc.* and package.json files.

Example:

eslint --no-eslintrc file.js

-c, --config

This option allows you to specify an additional configuration file for ESLint (see Configuring ESLint for more).

Example:

eslint -c ~/my-eslint.json file.js

This example uses the configuration file at ~/my-eslint.json.

If .eslintrc.* and/or package.json files are also used for configuration (i.e., --no-eslintrc was not specified), the configurations will be merged. Options from this configuration file have precedence over the options from .eslintrc.* and package.json files.

--env

This option enables specific environments. Details about the global variables defined by each environment are available on the Specifying Environments documentation. This option only enables environments; it does not disable environments set in other configuration files. To specify multiple environments, separate them using commas, or use the option multiple times.

Examples:

eslint --env browser,node file.js
eslint --env browser --env node file.js

--ext

This option allows you to specify which file extensions ESLint will use when searching for target files in the directories you specify. By default, ESLint lints *.js files and the files that match the overrides entries of your configuration.

Examples:

# Use only .ts extension
eslint . --ext .ts

# Use both .js and .ts
eslint . --ext .js --ext .ts

# Also use both .js and .ts
eslint . --ext .js,.ts

Note: --ext is only used when the arguments are directories. If you use glob patterns or file names, then --ext is ignored.

For example, eslint lib/* --ext .js will match all files within the lib/ directory, regardless of extension.

--global

This option defines global variables so that they will not be flagged as undefined by the no-undef rule. Any specified global variables are assumed to be read-only by default, but appending :true to a variable's name ensures that no-undef will also allow writes. To specify multiple global variables, separate them using commas, or use the option multiple times.

Examples:

eslint --global require,exports:true file.js
eslint --global require --global exports:true

--parser

This option allows you to specify a parser to be used by ESLint. By default, espree will be used.

--parser-options

This option allows you to specify parser options to be used by ESLint. Note that the available parser options are determined by the parser being used.

Examples:

echo '3 ** 4' | eslint --stdin --parser-options=ecmaVersion:6 # will fail with a parsing error
echo '3 ** 4' | eslint --stdin --parser-options=ecmaVersion:7 # succeeds, yay!

--resolve-plugins-relative-to

Changes the folder where plugins are resolved from. By default, plugins are resolved from the current working directory. This option should be used when plugins were installed by someone other than the end user. It should be set to the project directory of the project that has a dependency on the necessary plugins. For example:

• When using a config file that is located outside of the current project (with the --config flag), if the config uses plugins which are installed locally to itself, --resolve-plugins-relative-to should be set to the directory containing the config file.
• If an integration has dependencies on ESLint and a set of plugins, and the tool invokes ESLint on behalf of the user with a preset configuration, the tool should set --resolve-plugins-relative-to to the top-level directory of the tool.

Specifying rules and plugins

--rulesdir

This option allows you to specify another directory from which to load rules files. This allows you to dynamically load new rules at run time. This is useful when you have custom rules that aren't suitable for being bundled with ESLint.

Example:

eslint --rulesdir my-rules/ file.js

The rules in your custom rules directory must follow the same format as bundled rules to work properly. You can also specify multiple locations for custom rules by including multiple --rulesdir options:

eslint --rulesdir my-rules/ --rulesdir my-other-rules/ file.js

Note that, as with core rules and plugin rules, you still need to enable the rules in configuration or via the --rule CLI option in order to actually run those rules during linting. Specifying a rules directory with --rulesdir does not automatically enable the rules within that directory.

--plugin

This option specifies a plugin to load. You can omit the prefix eslint-plugin- from the plugin name.

Before using the plugin, you have to install it using npm.

Examples:

eslint --plugin jquery file.js
eslint --plugin eslint-plugin-mocha file.js

--rule

This option specifies rules to be used. These rules will be merged with any rules specified with configuration files. (You can use --no-eslintrc to change that behavior.) To define multiple rules, separate them using commas, or use the option multiple times. The levn format is used for specifying the rules.

If the rule is defined within a plugin, you have to prefix the rule ID with the plugin name and a /.

Examples:

eslint --rule 'quotes: [2, double]'
eslint --rule 'guard-for-in: 2' --rule 'brace-style: [2, 1tbs]'
eslint --rule 'jquery/dollar-sign: 2'

Fixing problems

--fix

This option instructs ESLint to try to fix as many issues as possible. The fixes are made to the actual files themselves and only the remaining unfixed issues are output. Not all problems are fixable using this option, and the option does not work in these situations:

1. This option throws an error when code is piped to ESLint.
2. This option has no effect on code that uses a processor, unless the processor opts into allowing autofixes.

If you want to fix code from stdin or otherwise want to get the fixes without actually writing them to the file, use the --fix-dry-run option.

--fix-dry-run

This option has the same effect as --fix with one difference: the fixes are not saved to the file system. This makes it possible to fix code from stdin (when used with the --stdin flag).

Because the default formatter does not output the fixed code, you'll have to use another one (e.g. json) to get the fixes. Here's an example of this pattern:

getSomeText | eslint --stdin --fix-dry-run --format=json

This flag can be useful for integrations (e.g. editor plugins) which need to autofix text from the command line without saving it to the filesystem.

--fix-type

This option allows you to specify the type of fixes to apply when using either --fix or --fix-dry-run. The four types of fixes are:

1. problem - fix potential errors in the code
2. suggestion - apply fixes to the code that improve it
3. layout - apply fixes that do not change the program structure (AST)
4. directive - apply fixes to inline directives such as // eslint-disable

You can specify one or more fix type on the command line. Here are some examples:

eslint --fix --fix-type suggestion .
eslint --fix --fix-type suggestion --fix-type problem .
eslint --fix --fix-type suggestion,layout .

This option is helpful if you are using another program to format your code but you would still like ESLint to apply other types of fixes.

Ignoring files

--ignore-path

This option allows you to specify the file to use as your .eslintignore. By default, ESLint looks in the current working directory for .eslintignore. You can override this behavior by providing a path to a different file.

Example:

eslint --ignore-path tmp/.eslintignore file.js
eslint --ignore-path .gitignore file.js

--no-ignore

Disables excluding of files from .eslintignore, --ignore-path, --ignore-pattern, and ignorePatterns property in config files.

Example:

eslint --no-ignore file.js

--ignore-pattern

This option allows you to specify patterns of files to ignore (in addition to those in .eslintignore). You can repeat the option to provide multiple patterns. The supported syntax is the same as for .eslintignore files, which use the same patterns as the .gitignore specification. You should quote your patterns in order to avoid shell interpretation of glob patterns.

Example:

eslint --ignore-pattern '/lib/' --ignore-pattern '/src/vendor/*' .

Using stdin

--stdin

This option tells ESLint to read and lint source code from STDIN instead of from files. You can use this to pipe code to ESLint.

Example:

cat myfile.js | eslint --stdin

--stdin-filename

This option allows you to specify a filename to process STDIN as. This is useful when processing files from STDIN and you have rules which depend on the filename.

Example

cat myfile.js | eslint --stdin --stdin-filename=myfile.js

Handling warnings

--quiet

This option allows you to disable reporting on warnings. If you enable this option, only errors are reported by ESLint.

Example:

eslint --quiet file.js

--max-warnings

This option allows you to specify a warning threshold, which can be used to force ESLint to exit with an error status if there are too many warning-level rule violations in your project.

Normally, if ESLint runs and finds no errors (only warnings), it will exit with a success exit status. However, if --max-warnings is specified and the total warning count is greater than the specified threshold, ESLint will exit with an error status. Specifying a threshold of -1 or omitting this option will prevent this behavior.

Example:

eslint --max-warnings 10 file.js

Output

-o, --output-file

Enable report to be written to a file.

Example:

eslint -o ./test/test.html

When specified, the given format is output into the provided file name.

-f, --format

This option specifies the output format for the console. Possible formats are:

• checkstyle
• compact
• html
• jslint-xml
• json
• junit
• stylish (the default)
• tap
• unix
• visualstudio

Example:

eslint -f compact file.js

You can also use a custom formatter from the command line by specifying a path to the custom formatter file.

Example:

eslint -f ./customformat.js file.js

An npm-installed formatter is resolved with or without eslint-formatter- prefix.

Example:

npm install eslint-formatter-pretty

eslint -f pretty file.js

// equivalent:
eslint -f eslint-formatter-pretty file.js

When specified, the given format is output to the console. If you'd like to save that output into a file, you can do so on the command line like so:

eslint -f compact file.js > results.txt

This saves the output into the results.txt file.

--color, --no-color

This option forces the enabling/disabling of colorized output. You can use this to override the default behavior, which is to enable colorized output unless no TTY is detected, such as when piping eslint through cat or less.

Examples:

eslint --color file.js | cat
eslint --no-color file.js

Inline configuration comments

--no-inline-config

This option prevents inline comments like /*eslint-disable*/ or /*global foo*/ from having any effect. This allows you to set an ESLint config without files modifying it. All inline config comments are ignored, e.g.:

• /*eslint-disable*/
• /*eslint-enable*/
• /*global*/
• /*eslint*/
• /*eslint-env*/
• // eslint-disable-line
• // eslint-disable-next-line

Example:

eslint --no-inline-config file.js

--report-unused-disable-directives

This option causes ESLint to report directive comments like // eslint-disable-line when no errors would have been reported on that line anyway. This can be useful to prevent future errors from unexpectedly being suppressed, by cleaning up old eslint-disable comments which are no longer applicable.

Warning: When using this option, it is possible that new errors will start being reported whenever ESLint or custom rules are upgraded. For example, suppose a rule has a bug that causes it to report a false positive, and an eslint-disable comment is added to suppress the incorrect report. If the bug is then fixed in a patch release of ESLint, the eslint-disable comment will become unused since ESLint is no longer generating an incorrect report. This will result in a new reported error for the unused directive if the report-unused-disable-directives option is used.

Example:

eslint --report-unused-disable-directives file.js

Caching

--cache

Store the info about processed files in order to only operate on the changed ones. The cache is stored in .eslintcache by default. Enabling this option can dramatically improve ESLint's running time by ensuring that only changed files are linted.

Note: If you run ESLint with --cache and then run ESLint without --cache, the .eslintcache file will be deleted. This is necessary because the results of the lint might change and make .eslintcache invalid. If you want to control when the cache file is deleted, then use --cache-location to specify an alternate location for the cache file.

Note: Autofixed files are not placed in the cache. Subsequent linting that does not trigger an autofix will place it in the cache.

--cache-file

Path to the cache file. If none specified .eslintcache will be used. The file will be created in the directory where the eslint command is executed. Deprecated: Use --cache-location instead.

--cache-location

Path to the cache location. Can be a file or a directory. If no location is specified, .eslintcache will be used. In that case, the file will be created in the directory where the eslint command is executed.

If a directory is specified, a cache file will be created inside the specified folder. The name of the file will be based on the hash of the current working directory (CWD). e.g.: .cache_hashOfCWD

Important note: If the directory for the cache does not exist make sure you add a trailing / on *nix systems or \ in windows. Otherwise the path will be assumed to be a file.

Example:

eslint "src/**/*.js" --cache --cache-location "/Users/user/.eslintcache/"

--cache-strategy

Strategy for the cache to use for detecting changed files. Can be either metadata or content. If no strategy is specified, metadata will be used.

The content strategy can be useful in cases where the modification time of your files change even if their contents have not. For example, this can happen during git operations like git clone because git does not track file modification time.

Example:

eslint "src/**/*.js" --cache --cache-strategy content

Miscellaneous

--init

This option will start config initialization wizard. It's designed to help new users quickly create .eslintrc file by answering a few questions, choosing a popular style guide, or inspecting your source files and attempting to automatically generate a suitable configuration.

The resulting configuration file will be created in the current directory.

--env-info

This option outputs information about the execution environment, including the version of Node, npm, and local and global installations of ESLint. The ESLint team may ask for this information to help solve bugs.

--no-error-on-unmatched-pattern

This option prevents errors when a quoted glob pattern or --ext is unmatched. This will not prevent errors when your shell can't match a glob.

--exit-on-fatal-error

This option causes ESLint to exit with exit code 2 if one or more fatal parsing errors occur. Without this option, fatal parsing errors are reported as rule violations.

--debug

This option outputs debugging information to the console. This information is useful when you're seeing a problem and having a hard time pinpointing it. The ESLint team may ask for this debugging information to help solve bugs.

-h, --help

This option outputs the help menu, displaying all of the available options. All other options are ignored when this is present.

-v, --version

This option outputs the current ESLint version onto the console. All other options are ignored when this is present.

--print-config

This option outputs the configuration to be used for the file passed. When present, no linting is performed and only config-related options are valid.

Example:

eslint --print-config file.js

Ignoring files from linting

ESLint supports .eslintignore files to exclude files from the linting process when ESLint operates on a directory. Files given as individual CLI arguments will be exempt from exclusion. The .eslintignore file is a plain text file containing one pattern per line. It can be located in any of the target directory's ancestors; it will affect files in its containing directory as well as all sub-directories. Here's a simple example of a .eslintignore file:

temp.js
**/vendor/*.js

A more detailed breakdown of supported patterns and directories ESLint ignores by default can be found in Ignoring Code.

Exit codes

When linting files, ESLint will exit with one of the following exit codes:

• 0: Linting was successful and there are no linting errors. If the --max-warnings flag is set to n, the number of linting warnings is at most n.
• 1: Linting was successful and there is at least one linting error, or there are more linting warnings than allowed by the --max-warnings option.
• 2: Linting was unsuccessful due to a configuration problem or an internal error.