[SOLVED] trap ignoring exit signal

Issue

I have a simple bash script:

#!/bin/bash
# Zip data and upload it to a cloud storage provider

set -euo pipefail

# some config and funcs removed, only relevant are left.
file=foo
dest=bar
temp_dir=$(mktemp -d)

fail() {
    log "$1"
    exit 1
}

log() {
    echo "$(date) - $1"
    echo "$1" | systemd-cat -p notice -t cloud_archive
}

put_archive() {
    # Put archives into storage.
    # This is where we fail
    cp "${file}" "${dest}" || fail "Uploading failed"
}

cleanup() {
  # remove some temp files etc.
  # and send message to stdout and journal
  log "Deleting temp dir ${temp_dir}."
  rm -r "${temp_dir}"
}

put_archive
trap cleanup EXIT

From my understanding this is the basic use case for a bash trap. The cp command fails with $? != 0, triggering the fail function, which in turn sends a log message to the journal and then exit 1. The trap should catch that signal and fire cleanup. That part is what does not work. The script just exits with log message "Uploading failed" and does not fire cleanup. I do not see the log output from that function and temp_dir still exists.

What I did:

• Remove set -euo pipefail
• Add set -x to verify executed commands, which did not result in anything useful
• There are no subshells which might interfere with the trap
• trap is not used within a function which could have been not yet defined when the script exits

I am having a hard time understanding what I am doing wrong. What am I not seeing here?

Solution

Just place trap directive line before running your put_archive function!!

Otherwise, if your function fail, your fail function will exit your script before executing trap directive.

fail() {
    log "$1"
    exit 1
}
put_archive() {
    something || || fail "some message"
}

trap cleanup EXIT

put_archive

But you could build another exit way:

fail() {
    log "$1"
    cleanup 1
}
log() {
    echo "$(date) - $1"
    echo "$1" | systemd-cat -p notice -t cloud_archive
}
cleanup() {
    log "Deleting temp dir ${temp_dir}."
    rm -r "${temp_dir}"
    exit ${1:-0}
}
put_archive() {
    cp "${file}" "${dest}" ||
        fail "Uploading failed"
}

put_archive
cleanup

Doing so, you don't need to use trap directive.

Answered By - F. Hauri - Give Up GitHub

Answer Checked By - Timothy Miller (WPSolving Admin)