Use shellcheck!

shellcheck is a super useful linter for your shell scripts.

I say shell scripts instead of bash scripts since you should typically avoid using bash to run your scripts, since bash:

• Includes functionality that isn’t POSIX compliant, which risks portability.
• Is slower than dash, which is POSIX compliant and includes no extra features.
• Has idiosyncrasies, typically called bash-isms, that manage to creep their way into regular shell scripts

The above reasons are why you should put #!/bin/sh at the top of your scripts, and not #!/bin/bash. On Debian systems /bin/sh is symlinked to /bin/dash so that your scripts run as fast as possible. On other distros it might be linked to something else, but I highly recommend linking it to dash.

Note: /bin/sh being linked to another shell is entirely different from your login shell. You can still use whatever login shell you want, I use fish for example, without it affecting your scripts. The scripts will still be invoked with a POSIX compliant shell.

Anyway. shellcheck helps you write POSIX compliant scripts, or will let you specify #!/bin/bash and use all the bash-isms you want. It also has detailed descriptions and justifications of its warnings on their wiki

Writing shell scripts comes with a lot of foot-guns. shellcheck can help remove some of these, provided you heed its warnings!

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