ShellCheck supports additional checks that are not enabled by default. These are generally subjective or stylistic.
Checks can be enabled with flags or an enable
directive in the file or
.shellcheckrc
:
#!/bin/sh
# shellcheck enable=require-variable-braces
echo "$RANDOM" # Will emit a suggestion to use `${RANDOM}`
or put enable=require-variable-braces
in a
.shellcheckrc
in your home directory or project root.
They can also be enabled on the command-line with
-o
:
$ shellcheck -o require-variable-braces myscript
It's a good idea to enable all warnings with -Wall
in C,
but this is not the case in ShellCheck. Optional checks are more
subjective rather than more comprehensive, and may conflict with each
other.
However, if you for debugging or evaluation purposes want to see
what's available, you can enable them with -o all
or
enable=all
as above.
To see which checks are available in your version of ShellCheck, use
the --list-optional
flag.
Optional checks as of version 0.10.0:
$ shellcheck --list-optional
name: add-default-case
desc: Suggest adding a default case in `case` statements
example: case $? in 0) echo 'Success';; esac
fix: case $? in 0) echo 'Success';; *) echo 'Fail' ;; esac
name: avoid-nullary-conditions
desc: Suggest explicitly using -n in `[ $var ]`
example: [ "$var" ]
fix: [ -n "$var" ]
name: check-extra-masked-returns
desc: Check for additional cases where exit codes are masked
example: rm -r "$(get_chroot_dir)/home"
fix: set -e; dir="$(get_chroot_dir)"; rm -r "$dir/home"
name: check-set-e-suppressed
desc: Notify when set -e is suppressed during function invocation
example: set -e; func() { cp *.txt ~/backup; rm *.txt; }; func && echo ok
fix: set -e; func() { cp *.txt ~/backup; rm *.txt; }; func; echo ok
name: check-unassigned-uppercase
desc: Warn when uppercase variables are unassigned
example: echo $VAR
fix: VAR=hello; echo $VAR
name: deprecate-which
desc: Suggest 'command -v' instead of 'which'
example: which javac
fix: command -v javac
name: quote-safe-variables
desc: Suggest quoting variables without metacharacters
example: var=hello; echo $var
fix: var=hello; echo "$var"
name: require-double-brackets
desc: Require [[ and warn about [ in Bash/Ksh
example: [ -e /etc/issue ]
fix: [[ -e /etc/issue ]]
name: require-variable-braces
desc: Suggest putting braces around all variable references
example: var=hello; echo $var
fix: var=hello; echo ${var}
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.