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% SHELLCHECK(1) Shell script analysis tool

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.

-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.

--norc

: Don't try to look for .shellcheckrc configuration files.

-P\ SOURCEPATH,\ **--source-path=**SOURCEPATH

: Specify paths to search for sourced files, separated by : on Unix and ; on Windows. Absolute paths will also be rooted in these. The special path SCRIPTDIR can be used to specify the currently checked script's directory, as in -P SCRIPTDIR or -P SCRIPTDIR/../libs. Subsequent -P flags accumulate and take predecence.

-S\ SEVERITY,\ **--severity=**severity

: Specify minimum severity of errors to consider. Valid values in order of severity are error, warning, info, style and verbose. The default is style.

-s\ shell,\ **--shell=**shell

: Specify Bourne shell dialect. Valid values are sh, bash, dash and ksh. The default is to deduce the shell from the file's shell directive, shebang, or .bash/.bats/.dash/.ksh extension, in that order.

-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.

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>

json

: Json is a popular serialization format that is more suitable for web applications. ShellCheck's json is compact and contains only the bare minimum.

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

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 before a 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.

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.

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=2039'.

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:

# Don't suggest using -n in [ $var ]
disable=SC2244

# Allow using `which` since it gives full paths and is common enough
disable=SC2230

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 follow 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.

AUTHOR

ShellCheck is written and maintained by Vidar Holen.

REPORTING BUGS

Bugs and issues can be reported on GitHub:

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

COPYRIGHT

Copyright 2012-2015, Vidar Holen. Licensed under the GNU General Public License version 3 or later, see https://gnu.org/licenses/gpl.html

SEE ALSO

sh(1) bash(1)