SHELLCHECK(1)

NAME
shellcheck - Shell script analysis tool

SYNOPSIS
shellcheck [OPTIONS...] FILES...

DESCRIPTION
ShellCheck is a static analysis and linting tool for sh/bash scripts. It's mainly focused on handling typical beginner and intermediate level syntax errors and pitfalls where the shell just gives a cryptic error message or strange behavior, but it also reports on a few more advanced issues where corner cases can cause delayed failures.

ShellCheck gives shell specific advice. Consider this line:

        (( area = 3.14*r*r ))

•   For scripts starting with #!/bin/sh (or when using -s sh), ShellCheck will warn that (( .. )) is not POSIX compliant (similar to checkbashisms).

•   For scripts starting with #!/bin/bash (or using -s bash), ShellCheck will warn that decimals are not supported.

•   For scripts starting with #!/bin/ksh (or using -s ksh), ShellCheck will not warn at all, as ksh supports decimals in arithmetic contexts.

OPTIONS

-a, --check-sourced
    Emit warnings in sourced files. Normally, shellcheck will only warn about issues in the specified files. With this option, any issues in sourced files will also be reported.

-C[WHEN], --color[=WHEN]
    For TTY output, enable colors always, never or auto. The default is auto. --color without an argument is equivalent to --color=always.

-i CODE1[,CODE2...], --include=CODE1[,CODE2...]
    Explicitly include only the specified codes in the report. Subsequent -i options are cumulative, but all the codes can be specified at once, comma-separated as a single argument. Include options override any provided exclude options.

-e CODE1[,CODE2...], --exclude=CODE1[,CODE2...]
    Explicitly exclude the specified codes from the report. Subsequent -e options are cumulative, but all the codes can be specified at once, comma-separated as a single argument.

--extended-analysis=true/false
    Enable/disable Dataflow Analysis to identify more issues (default true). If ShellCheck uses too much CPU/RAM when checking scripts with several thousand lines of code, extended analysis can be disabled with this flag or a directive. This flag overrides directives and rc files.

-f FORMAT, --format=FORMAT
    Specify the output format of shellcheck, which prints its results in the standard output. Subsequent -f options are ignored, see FORMATS below for more information.

--list-optional
    Output a list of known optional checks. These can be enabled with -o flags or enable directives.

--norc
    Don't try to look for .shellcheckrc configuration files.

--rcfile RCFILE
    Prefer the specified configuration file over searching for one in the default locations.

-o NAME1[,NAME2...], --enable=NAME1[,NAME2...]
    Enable optional checks. The special name all enables all of them. Subsequent -o options accumulate. This is equivalent to specifying enable directives.

-P SOURCEPATH, --source-path=SOURCEPATH
    Specify paths to search for sourced files, separated by : on Unix and ; on Windows. This is equivalent to specifying search-path directives.

-s shell, --shell=shell
    Specify Bourne shell dialect. Valid values are sh, bash, dash, ksh, and busybox. The default is to deduce the shell from the file's shell directive, shebang, or .bash/.bats/.dash/.ksh extension, in that order. sh refers to POSIX sh (not the system's), and will warn of portability issues.

-S SEVERITY, --severity=severity
    Specify minimum severity of errors to consider. Valid values in order of severity are error, warning, info and style. The default is style.

-V, --version
    Print version information and exit.

-W NUM, --wiki-link-count=NUM
    For TTY output, show NUM wiki links to more information about mentioned warnings. Set to 0 to disable them entirely.

-x, --external-sources
    Follow source statements even when the file is not specified as input. By default, shellcheck will only follow files specified on the command line (plus /dev/null). This option allows following any file the script may source.

    This option may also be enabled using external-sources=true in .shellcheckrc. This flag takes precedence.

FILES...
    One or more script files to check, or "-" for standard input.

FORMATS

tty Plain text, human readable output. This is the default.

gcc GCC compatible output. Useful for editors that support compiling and showing syntax errors.

    For example, in Vim, :set makeprg=shellcheck\ -f\ gcc\ % will allow using :make to check the script, and :cnext to jump to the next error.

            <file>:<line>:<column>: <type>: <message>

checkstyle
    Checkstyle compatible XML output. Supported directly or through plugins by many IDEs and build monitoring systems.

            <?xml version='1.0' encoding='UTF-8'?>
            <checkstyle version='4.3'>
              <file name='file'>
                <error
                  line='line'
                  column='column'
                  severity='severity'
                  message='message'
                  source='ShellCheck.SC####' />
                ...
              </file>
              ...
            </checkstyle>

diff
    Auto-fixes in unified diff format. Can be piped to git apply or patch -p1 to automatically apply fixes.

            --- a/test.sh
            +++ b/test.sh
            @@ -2,6 +2,6 @@
             ## Example of a broken script.
             for f in $(ls *.m3u)
             do
            -  grep -qi hq.*mp3 $f \
            +  grep -qi hq.*mp3 "$f" \
                 && echo -e 'Playlist $f contains a HQ file in mp3 format'
             done

json1
    Json is a popular serialization format that is more suitable for web applications. ShellCheck's json is compact and contains only the bare minimum. Tabs are counted as 1 character.

            {
              comments: [
                {
                  "file": "filename",
                  "line": lineNumber,
                  "column": columnNumber,
                  "level": "severitylevel",
                  "code": errorCode,
                  "message": "warning message"
                },
                ...
              ]
            }

json
    This is a legacy version of the json1 format. It's a raw array of comments, and all offsets have a tab stop of 8.

quiet
    Suppress all normal output. Exit with zero if no issues are found, otherwise exit with one. Stops processing after the first issue.

DIRECTIVES
ShellCheck directives can be specified as comments in the shell script. If they appear before the first command, they are considered file-wide. Otherwise, they apply to the immediately following command or block:

        # shellcheck key=value key=value
        command-or-structure

For example, to suppress SC2035 about using ./*.jpg:

        # shellcheck disable=SC2035
        echo "Files: " *.jpg

To tell ShellCheck where to look for an otherwise dynamically determined file:

        # shellcheck source=./lib.sh
        source "$(find_install_dir)/lib.sh"

Here a shell brace group is used to suppress a warning on multiple lines:

        # shellcheck disable=SC2016
        {
          echo 'Modifying $PATH'
          echo 'PATH=foo:$PATH' >> ~/.bashrc
        }

Valid keys are:

disable
    Disables a comma separated list of error codes for the following command. The command can be a simple command like echo foo, or a compound command like a function definition, subshell block or loop. A range can be be specified with a dash, e.g. disable=SC3000-SC4000 to exclude 3xxx. All warnings can be disabled with disable=all.

enable
    Enable an optional check by name, as listed with --list-optional. Only file-wide enable directives are considered.

extended-analysis
    Set to true/false to enable/disable dataflow analysis. Specifying # shellcheck extended-analysis=false in particularly large (2000+ line) auto-generated scripts will reduce ShellCheck's resource usage at the expense of certain checks. Extended analysis is enabled by default.

external-sources
    Set to true in .shellcheckrc to always allow ShellCheck to open arbitrary files from 'source' statements (the way most tools do).

    This option defaults to false only due to ShellCheck's origin as a remote service for checking untrusted scripts. It can safely be enabled for normal development.

source
    Overrides the filename included by a source/. statement. This can be used to tell shellcheck where to look for a file whose name is determined at runtime, or to skip a source by telling it to use /dev/null.

source-path
    Add a directory to the search path for source/. statements (by default, only ShellCheck's working directory is included). Absolute paths will also be rooted in these paths. The special path SCRIPTDIR can be used to specify the currently checked script's directory, as in source-path=SCRIPTDIR or source-path=SCRIPTDIR/../libs. Multiple paths accumulate, and -P takes precedence over them.

shell
    Overrides the shell detected from the shebang. This is useful for files meant to be included (and thus lacking a shebang), or possibly as a more targeted alternative to 'disable=SC2039'.

RC FILES
Unless --norc is used, ShellCheck will look for a file .shellcheckrc or shellcheckrc in the script's directory and each parent directory. If found, it will read key=value pairs from it and treat them as file-wide directives.

Here is an example .shellcheckrc:

        # Look for 'source'd files relative to the checked script,
        # and also look for absolute paths in /mnt/chroot
        source-path=SCRIPTDIR
        source-path=/mnt/chroot
        # Since 0.9.0, values can be quoted with '' or "" to allow spaces
        source-path="My Documents/scripts"
        # Allow opening any 'source'd file, even if not specified as input
        external-sources=true
        # Turn on warnings for unquoted variables with safe values
        enable=quote-safe-variables
        # Turn on warnings for unassigned uppercase variables
        enable=check-unassigned-uppercase
        # Allow [ ! -z foo ] instead of suggesting -n
        disable=SC2236

If no .shellcheckrc is found in any of the parent directories, ShellCheck will look in ~/.shellcheckrc followed by the XDG config directory (usually ~/.config/shellcheckrc) on Unix, or %APPDATA%/shellcheckrc on Windows. Only the first file found will be used.

Note for Snap users: the Snap sandbox disallows access to hidden files. Use shellcheckrc without the dot instead.

Note for Docker users: ShellCheck will only be able to look for files that are mounted in the container, so ~/.shellcheckrc will not be read.

ENVIRONMENT VARIABLES
The environment variable SHELLCHECK_OPTS can be set with default flags:

        export SHELLCHECK_OPTS='--shell=bash --exclude=SC2016'

Its value will be split on spaces and prepended to the command line on each invocation.

RETURN VALUES
ShellCheck uses the following exit codes:

•   0: All files successfully scanned with no issues.

•   1: All files successfully scanned with some issues.

•   2: Some files could not be processed (e.g. file not found).

•   3: ShellCheck was invoked with bad syntax (e.g. unknown flag).

•   4: ShellCheck was invoked with bad options (e.g. unknown formatter).

LOCALE
This version of ShellCheck is only available in English. All files are leniently decoded as UTF-8, with a fallback of ISO-8859-1 for invalid sequences. LC_CTYPE is respected for output, and defaults to UTF-8 for locales where encoding is unspecified (such as the C locale).

Windows users seeing commitBuffer: invalid argument (invalid character) should set their terminal to use UTF-8 with chcp 65001.

KNOWN INCOMPATIBILITIES
(If nothing in this section makes sense, you are unlikely to be affected by it)

To avoid confusing and misguided suggestions, ShellCheck requires function bodies to be either { brace groups; } or ( subshells ), and function names containing []*=! are only recognized after a function keyword.

The following unconventional function definitions are identical in Bash, but ShellCheck only recognizes the latter.

        [x!=y] () [[ $1 ]]
        function [x!=y] () { [[ $1 ]]; }

Shells without the function keyword do not allow these characters in function names to begin with. Function names containing {} are not supported at all.

Further, if ShellCheck sees [x!=y] it will assume this is an invalid comparison. To invoke the above function, quote the command as in '[x!=y]', or to retain the same globbing behavior, use command [x!=y].

ShellCheck imposes additional restrictions on the [ command to help diagnose common invalid uses. While [ $x= 1 ] is defined in POSIX, ShellCheck will assume it was intended as the much more likely comparison [ "$x" = 1 ] and fail accordingly. For unconventional or dynamic uses of the [ command, use test or \[ instead.

REPORTING BUGS
Bugs and issues can be reported on GitHub:

https://github.com/koalaman/shellcheck/issues

AUTHORS
ShellCheck is developed and maintained by Vidar Holen, with assistance from a long list of wonderful contributors.

COPYRIGHT
Copyright 2012-2024, Vidar Holen and contributors. Licensed under the GNU General Public License version 3 or later, see https://gnu.org/licenses/gpl.html

SEE ALSO
sh(1) bash(1)