Command line interface

luacheck program accepts files, directories and rockspecs as arguments. They can be filtered using --include-files and --exclude-files options, see below.

  • Given a file, luacheck will check it.
  • Given -, luacheck will check stdin.
  • Given a directory, luacheck will check all files within it, selecting only files with .lua extension unless --include-files option is used. This feature requires LuaFileSystem (installed automatically if LuaRocks was used to install Luacheck).
  • Given a rockspec (a file with .rockspec extension), luacheck will check all files with .lua extension mentioned in the rockspec in build.install.lua, build.install.bin and build.modules tables.

The output of luacheck consists of separate reports for each checked file and ends with a summary:

$ luacheck src
Checking src/bad_code.lua                         5 warnings

    src/bad_code.lua:3:16: unused variable helper
    src/bad_code.lua:3:23: unused variable length argument
    src/bad_code.lua:7:10: setting non-standard global variable embrace
    src/bad_code.lua:8:10: variable opt was previously defined as an argument on line 7
    src/bad_code.lua:9:11: accessing undefined variable hepler

Checking src/good_code.lua                        OK
Checking src/python_code.lua                      1 error

    src/python_code.lua:1:6: expected '=' near '__future__'

Checking src/unused_code.lua                      9 warnings

    src/unused_code.lua:3:18: unused argument baz
    src/unused_code.lua:4:8: unused loop variable i
    src/unused_code.lua:5:13: unused variable q
    src/unused_code.lua:7:11: unused loop variable a
    src/unused_code.lua:7:14: unused loop variable b
    src/unused_code.lua:7:17: unused loop variable c
    src/unused_code.lua:13:7: value assigned to variable x is unused
    src/unused_code.lua:14:1: value assigned to variable x is unused
    src/unused_code.lua:22:1: value assigned to variable z is unused

Total: 14 warnings / 1 error in 4 files

luacheck chooses exit code as follows:

  • Exit code is 0 if no warnings or errors occurred.
  • Exit code is 1 if some warnings occured but there were no syntax errors or invalid inline options.
  • Exit code is 2 if there were some syntax errors or invalid inline options.
  • Exit code is 3 if some files couldn’t be checked, typically due to an incorrect file name.
  • Exit code is 4 if there was a critical error (invalid CLI arguments, config, or cache file).

Command line options

Short options that do not take an argument can be combined into one, so that -qqu is equivalent to -q -q -u. For long options, both --option value or --option=value can be used.

Options taking several arguments can be used several times; --ignore foo --ignore bar is equivalent to --ignore foo bar.

Note that options that may take several arguments, such as --globals, should not be used immediately before positional arguments; given --globals foo bar file.lua, luacheck will consider all foo, bar and file.lua global and then panic as there are no file names left.

Option Meaning
-g | --no-global Filter out warnings related to global variables.
-u | --no-unused Filter out warnings related to unused variables and values.
-r | --no-redefined Filter out warnings related to redefined variables.
-a | --no-unused-args Filter out warnings related to unused arguments and loop variables.
-s | --no-unused-secondaries

Filter out warnings related to unused variables set together with used ones.

See Secondary values and variables

--no-self Filter out warnings related to implicit self argument.
--std <std>

Set standard globals. <std> can be one of:

  • lua51 - globals of Lua 5.1 without deprecated ones;
  • lua51c - globals of Lua 5.1;
  • lua52 - globals of Lua 5.2;
  • lua52c - globals of Lua 5.2 compiled with LUA_COMPAT_ALL;
  • lua53 - globals of Lua 5.3;
  • lua53c - globals of Lua 5.3 compiled with LUA_COMPAT_5_2;
  • luajit - globals of LuaJIT 2.x;
  • ngx_lua - globals of Openresty lua-nginx-module 0.10.10, including standard LuaJIT 2.x globals;
  • min - intersection of globals of Lua 5.1, Lua 5.2, Lua 5.3 and LuaJIT 2.x;
  • max - union of globals of Lua 5.1, Lua 5.2, Lua 5.3 and LuaJIT 2.x;
  • _G (default) - same as lua51c, lua52c, lua53c, or luajit depending on version of Lua used to run luacheck or same as max if couldn’t detect the version;
  • love - globals added by LÖVE (love2d);
  • busted - globals added by Busted 2.0;
  • rockspec - globals allowed in rockspecs;
  • none - no standard globals.

See Sets of standard globals

--globals [<name>] ... Add custom global variables or fields on top of standard ones. See Defining extra globals and fields
--read-globals [<name>] ... Add read-only global variables or fields.
--new-globals [<name>] ... Set custom global variables or fields. Removes custom globals added previously.
--new-read-globals [<name>] ... Set read-only global variables or fields. Removes read-only globals added previously.
--not-globals [<name>] ... Remove custom and standard global variables or fields.
-c | --compat Equivalent to --std max.
-d | --allow-defined

Allow defining globals implicitly by setting them.

See Implicitly defined globals

-t | --allow-defined-top

Allow defining globals implicitly by setting them in the top level scope.

See Implicitly defined globals

-m | --module

Limit visibility of implicitly defined globals to their files.

See Modules

--max-line-length <length Set maximum allowed line length (default: 120).
--no-max-line-length Do not limit line length.
--max-code-line-length <length Set maximum allowed length for lines ending with code (default: 120).
--no-max-code-line-length Do not limit code line length.
--max-string-line-length <length Set maximum allowed length for lines within a string (default: 120).
--no-max-string-line-length Do not limit string line length.
--max-comment-line-length <length Set maximum allowed length for comment lines (default: 120).
--no-max-comment-line-length Do not limit comment line length.
--ignore | -i <patt> [<patt>] ... Filter out warnings matching patterns.
--enable | -e <patt> [<patt>] ... Do not filter out warnings matching patterns.
--only | -o <patt> [<patt>] ... Filter out warnings not matching patterns.
--no-inline Disable inline options.
--config <config> Path to custom configuration file (default: .luacheckrc).
--no-config Do not look up custom configuration file.
--default-config <config>

Default path to custom configuration file, to be used if --[no-]config is not used and .luacheckrc is not found.

Default global location is:

  • %LOCALAPPDATA%\Luacheck\.luacheckrc on Windows;
  • ~/Library/Application Support/Luacheck/.luacheckrc on OS X/macOS;
  • $XDG_CONFIG_HOME/luacheck/.luacheckrc or ~/.config/luacheck/.luacheckrc on other systems.
--no-default-config Do not use fallback configuration file.
--filename <filename> Use another filename in output, for selecting configuration overrides and for file filtering.
--exclude-files <glob> [<glob>] ... Do not check files matching these globbing patterns. Recursive globs such as **/*.lua are supported.
--include-files <glob> [<glob>] ... Do not check files not matching these globbing patterns.
--cache [<cache>] Path to cache file. (default: .luacheckcache). See Caching
--no-cache Do not use cache.
-j | --jobs Check <jobs> files in parallel. Requires LuaLanes. Default number of jobs is set to number of available processing units.
--formatter <formatter>

Use custom formatter. <formatter> must be a module name or one of:

  • TAP - Test Anything Protocol formatter;
  • JUnit - JUnit XML formatter;
  • plain - simple warning-per-line formatter;
  • default - standard formatter.
-q | --quiet

Suppress report output for files without warnings.

  • -qq - Suppress output of warnings.
  • -qqq - Only output summary.
--codes Show warning codes.
--ranges Show ranges of columns related to warnings.
--no-color Do not colorize output.
-v | --version Show version of Luacheck and its dependencies and exit.
-h | --help Show help and exit.

Patterns

CLI options --ignore, --enable and --only and corresponding config options allow filtering warnings using pattern matching on warning codes, variable names or both. If a pattern contains a slash, the part before slash matches warning code and the part after matches variable name. Otherwise, if a pattern contains a letter or underscore, it matches variable name. Otherwise, it matches warning code. E.g.:

Pattern Matching warnings
4.2 Shadowing declarations of arguments or redefining them.
.*_ Warnings related to variables with _ suffix.
4.2/.*_ Shadowing declarations of arguments with _ suffix or redefining them.

Unless already anchored, patterns matching variable names are anchored at both sides and patterns matching warning codes are anchored at their beginnings. This allows one to filter warnings by category (e.g. --only 1 focuses luacheck on global-related warnings).

Defining extra globals and fields

CLI options --globals, --new-globals, --read-globals, --new-read-globals, and corresponding config options add new allowed globals or fields. E.g. --read-globals foo --globals foo.bar allows accessing foo global and mutating its bar field. --not-globals also operates on globals and fields and removes definitions of both standard and custom globals.

Sets of standard globals

CLI option --stds allows combining built-in sets described above using +. For example, --std max is equivalent to --std=lua51c+lua52c+lua53c+luajit. Leading plus sign adds new sets to default one instead of replacing it. For instance, --std +busted is suitable for checking test files that use Busted testing framework. Custom sets of globals can be defined by mutating global variable stds in config. See Custom sets of globals

Formatters

CLI option --formatter allows selecting a custom formatter for luacheck output. A custom formatter is a Lua module returning a function with three arguments: report as returned by luacheck module (see Report format), array of file names and table of options. Options contain values assigned to quiet, color, limit, codes, ranges and formatter options in CLI or config. Formatter function must return a string.

Caching

If LuaFileSystem is available, Luacheck can cache results of checking files. On subsequent checks, only files which have changed since the last check will be rechecked, improving run time significantly. Changing options (e.g. defining additional globals) does not invalidate cache. Caching can be enabled by using --cache <cache> option or cache config option. Using --cache without an argument or setting cache config option to true sets .luacheckcache as the cache file. Note that --cache must be used every time luacheck is run, not on the first run only.

Stable interface for editor plugins and tools

Command-line interface of Luacheck can change between minor releases. Starting from 0.11.0 version, the following interface is guaranteed at least till 1.0.0 version, and should be used by tools using Luacheck output, e.g. editor plugins.

  • Luacheck should be started from the directory containing the checked file.
  • File can be passed through stdin using - as argument or using a temporary file. Real filename should be passed using --filename option.
  • Plain formatter should be used. It outputs one issue (warning or error) per line.
  • To get precise error location, --ranges option can be used. Each line starts with real filename (passed using --filename), followed by :<line>:<start_column>-<end_column>:, where <line> is line number on which issue occurred and <start_column>-<end_column> is inclusive range of columns of token related to issue. Numbering starts from 1. If --ranges is not used, end column and dash is not printed.
  • To get warning and error codes, --codes option can be used. For each line, substring between parentheses contains three digit issue code, prefixed with E for errors and W for warnings. Lack of such substring indicates a fatal error (e.g. I/O error).
  • The rest of the line is warning message.

If compatibility with older Luacheck version is desired, output of luacheck --help can be used to get its version. If it contains string 0.<minor>.<patch>, where <minor> is at least 11 and patch is any number, interface described above should be used.