How to trap exit code in Bash script

bash signals exit-code bash-trap
Dagang picture Dagang · Mar 15, 2011 · Viewed 49.4k times · Source

There're many exit points in my bash code. I need to do some clean up work on exit, so I used trap to add a callback for exit like this:

trap "mycleanup" EXIT

The problem is there're different exit codes, I need to do corresponding cleanup works. Can I get exit code in mycleanup?

Answer

Paul Tobias picture Paul Tobias · May 13, 2014

The accepted answer is basically correct, I just want to clarify things.

The following example works well:

#!/bin/bash

cleanup() {
    rv=$?
    rm -rf "$tmpdir"
    exit $rv
}

tmpdir="$(mktemp)"
trap "cleanup" EXIT
# Do things...

But you have to be more careful if doing cleanup inline, without a function. For example this won't work:

trap "rv=$?; rm -rf $tmpdir; exit $rv" EXIT

Instead you have to escape the $rv and $? variables:

trap "rv=\$?; rm -rf $tmpdir; exit \$rv" EXIT

You might also want to escape $tmpdir, as it will get evaluated when the trap line gets executed and if the tmpdir value changes later that might not give the expected behaviour.

Edit: Use shellcheck to check your bash scripts and be aware of problems like this.

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