% 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 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.

-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.

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

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

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

: Specify Bourne shell dialect. Valid values are sh, bash, dash and ksh. The default is to use the file‘s shebang, or bash if the target shell can’t be determined.

-V,\ --version

: Print version information and exit.

-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"
      },
      ...
    ]

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’.

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)