Bash scripts are brittle – simple error handling in bash

24 points by Meetvelde 15 hours ago | 9 comments

moebrowne
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
  I agree, the moment bash script needs "if" statement, you are using wrong language.
  frou_dh
  Is that so? Sounds like this commandment has a lot of authority, I'd better start following it.
  cousinbryce
  You’re free to program in language with only one data type all you want!
  rascul
  Tcl is great
vdm
> We can assign the value of $? to an environment variable
exit_code is not an environment variable?
https://www.gnu.org/software/bash/manual/html_node/Shell-Par...
- Meetvelde
  Oops, pretty sure I meant a regular variable. Will modify the post, thanks for pointing this out.
hks0
I declare a `my_die() { echo "$" 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.

    #!/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.