SHELLCHECK(1) 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 check-
bashisms).
• 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 con-
texts.
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 de-
fault 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. Sub-
sequent -i options are cumulative, but all the codes can be
specified at once, comma-separated as a single argument. In-
clude options override any provided exclude options.
-e CODE1[,CODE2...], --exclude=CODE1[,CODE2...]
Explicitly exclude the specified codes from the report. Subse-
quent -e options are cumulative, but all the codes can be speci-
fied at once, comma-separated as a single argument.
-f FORMAT, --format=FORMAT
Specify the output format of shellcheck, which prints its re-
sults in the standard output. Subsequent -f options are ig-
nored, 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.
-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
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. 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 de-
fault 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 fol-
lowing 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 compil-
ing 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 $f contains a HQ file in mp3 format'
done
json1 Json is a popular serialization format that is more suitable for
web applications. ShellCheck's json is compact and contains on-
ly the bare minimum. Tabs are counted as 1 character.
{
comments: [
{
"file": "filename",
"line": lineNumber,
"column": columnNumber,
"level": "severitylevel",
"code": errorCode,
"message": "warning message"
},
...
]
}
json This is a legacy version of the json1 format. It's a raw array
of comments, and all offsets have a tab stop of 8.
quiet Suppress all normal output. Exit with zero if no issues are
found, otherwise exit with one. Stops processing after the
first issue.
DIRECTIVES
ShellCheck directives can be specified as comments in the shell script.
If they appear before the first command, they are considered file-wide.
Otherwise, they apply to the immediately following command or block:
# shellcheck key=value key=value
command-or-structure
For example, to suppress SC2035 about using ./*.jpg:
# shellcheck disable=SC2035
echo "Files: " *.jpg
To tell ShellCheck where to look for an otherwise dynamically deter-
mined file:
# shellcheck source=./lib.sh
source "$(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. dis-
able=SC3000-SC4000 to exclude 3xxx. All warnings can be dis-
abled with disable=all.
enable Enable an optional check by name, as listed with --list-option-
al. Only file-wide enable directives are considered.
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). Ab-
solute 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 di-
rectory (usually ~/.config/shellcheckrc) on Unix, or %APPDA-
TA%/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 affect-
ed by it)
To avoid confusing and misguided suggestions, ShellCheck requires func-
tion bodies to be either { brace groups; } or ( subshells ), and func-
tion names containing []*=! are only recognized after a function key-
word.
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 di-
agnose common invalid uses. While [ $x= 1 ] is defined in POSIX,
ShellCheck will assume it was intended as the much more likely compari-
son [ "$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 2012-2022, Vidar Holen and contributors. Licensed under the
GNU General Public License version 3 or later, see https://gnu.org/li-
censes/gpl.html
SEE ALSO
sh(1) bash(1)
Shell script analysis tool SHELLCHECK(1)
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