access return code of a function from within the trap RETURN handler

Question

Within bash, how can a RETURN handler access the current return code?

For example

#!/usr/bin/env bash

function A() {
    function A_ret() {
        # How to access the return code here?
        echo "${FUNCNAME} ???"
    }
    trap A_ret RETURN
    echo -n "${FUNCNAME} returning code $1 ... "
    return $1
}
A 1

This prints

A returning code 1 ... A_ret ???

I would like it to print

A returning code 1 ... A_ret 1

How can A_ret access A return code?

Similar to this stackoverflow question Get the exitcode of the shell script in a “trap EXIT”.

Evaluate $? after you call your function within your script. — David C. Rankin
– David C. Rankin, Commented Aug 19, 2015 at 4:46
@DavidC.Rankin Per the title, the RETURN trap function, A_ret, needs to access the A return code. — JamesThomasMoon
– JamesThomasMoon, Commented Aug 19, 2015 at 8:08
Yes, I stumbled into that. Triplee straightened me out. As below, the return from trap will always be 0 unless there is a signal specification error. Good question. — David C. Rankin
– David C. Rankin, Commented Aug 19, 2015 at 8:11
If you are not using set -e, then the RETURN trap is called twice for a return statement, the first time, without $? set yet, and the second time with $? set according to the return statement. — Johan Boulé
– Johan Boulé, Commented Mar 11, 2023 at 0:09

chepner · Accepted Answer · 2015-08-19 13:16:41Z

5

It looks like the RETURN trap executes before the return statement actually sets the new value of $?. Consider this example that sets $? just before the return statement.

a () {
    a_ret () {
        echo "${FUNCNAME} $?"
    }
    trap a_ret RETURN
    printf "${FUNCNAME} returning code $1 ... "
    (exit 54)
    return $1
}

a 1

In bash 3.2 and 4.3, I get as output

a returning code 1 ... a_ret 54

I'd say this is a bug to report. As a workaround, you can always use the subshell exit with the value you intend to return:

a () {
    ...
    (exit $1)
    return $1
}

answered Aug 19, 2015 at 13:16

chepner

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