Bash scripts are brittle – simple error handling in bash

(notifox.com)

23 points | by Meetvelde 14 hours ago ago

7 comments

  • moebrowne 6 hours ago ago

    I believe that Bash scripts should be trivially short and simple. As soon as any complexity is introduced they should be written in another language.

    • general1465 5 hours ago ago

      I agree, the moment bash script needs "if" statement, you are using wrong language.

      • frou_dh 4 hours ago ago

        Is that so? Sounds like this commandment has a lot of authority, I'd better start following it.

  • vdm 8 hours ago ago

    > We can assign the value of $? to an environment variable

    exit_code is not an environment variable?

    https://www.gnu.org/software/bash/manual/html_node/Shell-Par...

    • Meetvelde 7 hours ago ago

      Oops, pretty sure I meant a regular variable. Will modify the post, thanks for pointing this out.

  • hks0 6 hours ago ago

    I declare a `my_die() { echo "$" 1>&2; exit 1; }` on top of each file. Makes life easier by knowing why the script failed instead of having only exit code or having to turn `set -x` on and rerun.

    Only if I could somehow mix `if` & `set -e`in a readable way... I wanted it to only capture errors of explicit `return 1` from bash functions, not from commands within those bash functions. But I guess I'm doing too much* of the job in bash now and it's getting messy.

  • burnt-resistor 2 hours ago ago

        #!/usr/bin/env bash
        set -eEuo pipefail # pipefail bash 4.2+, which is basically everything. There's a longer version for backwards compatibility, but it's rare.
    
        die() {
          echo >&2 "ERROR: $*"
          exit 1
        } 
    
        # e= & exit preserves the original exit code
        # trap - ... prevents multiple cleanup() calls
        # To only run on error instead of always, replace both EXITs with ERR
        trap 'e=$?; trap - EXIT; cleanup; exit $e' EXIT
        cleanup() {
          : # Delete this line and place cleanup code here.
        }
    
        # Minimal script here.
        # Use semantic-named functions.
        # DRY.
        # Don't use many levels of indentation.
        # All ordinary variables must be defined before use, so use checks like [[ -n "${X-}" ]]
        # All pipeline and bare command non-zero exit codes are errors.