Ubuntu Manpage: shellcheck - 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.

--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