Shell scripting is a must-have skill for DevOps. I used to be very very confident at Shell. But when I first tried ShellCheck, I realized that I’m just too proud and arrogant.
ShellCheck is a powerful code analysis tool for shell scripts. Like Pylint for Python or Rubocop for Ruby. Give it a try! You’ll get surprised.
ShellCheck helps to identify a lot of potential issues in your shell scripts. For example, here is one common mistake which ShellCheck reminds me. Mostly original code will work. However if we feed $dir with value like “My Documents”, it hurts. Sometime the bad code may incur very severe damage!
# Before: rm -rf $dir
# After: rm -rf "$dir"
Note: If you’re using Ruby heavily, check about this: Common Rubocop Errors.
ShellCheck is very easy to install and use. It is built and packaged using Cabal. We can install by apt-get/yum. Or use cabal-install directly like below. In mac OS, try “brew install shellcheck”.
# Install ShellCheck sudo apt-get install -y cabal-install sudo cabal update sudo cabal install shellcheck ln -s /root/.cabal/bin/shellcheck /usr/sbin/shellcheck # Example: Run check for Shell scripts sudo shellcheck my_script.sh
By default, ShellCheck enforces hundreds of rules. Each rule has a dedicated wiki page, which explains the purpose and improvement suggestion clearly.
For example, wiki for Rule SC1000: https://github…shellcheck/wiki/SC1000. I’m sure you can easily guess the wiki link of other rules.
Skip some ShellCheck rules, which don’t fit your projects. For your reference, here are rules I used to skip.
# Run test excluding certain rules EXCLUDE_CODE_LIST="SC1090,SC1091,SC2154,SC2001,SC2002" sudo shellcheck -e $EXCLUDE_CODE_LIST $file # Run test against all scripts under a folder EXCLUDE_CODE_LIST="SC1090,SC1091,SC2154,SC2001,SC2002" find . -name "*.sh" | xargs sudo \ shellcheck -e $EXCLUDE_CODE_LIST $file
Enforce Daily Shell Code Check by Jenkins. Enforce code quality check in your daily CI definitely helps.
Blog URL: https://www.dennyzhang.com/shellcheck
I really like the contents which you have mentioned. Thanks a lot.
This is a great idea. Is it specifically for bash or will it work on Korn shell scripts too but maybe with some limitations?
Jed, shellcheck should work for other shell, though I haven’t tried that.
Maybe you can have a try, and share your finding with us!