#!/bin/bash

#####################################################
# An example of using a trap to cleanup a temporary #
# even during errors or early script exit.          #
#####################################################

# an easy way to observe the tempfile:
#        watch "command ls -l -tc --reverse /tmp | tail"

declare sim_pipeerr=false
declare sim_earlyexit=false
declare -i do_something_delay=3

while true ; do
    case "$1" in
        -p)          sim_pipeerr=true           ; shift   ;;
        -e)          sim_earlyexit=true         ; shift   ;;
        -d)          do_something_delay=$2      ; shift 2 ;;
        -h | --help) echo "Usage: $0 [-p] [-e]" ; exit 0  ;;
        --) shift ; break ;;
        -*) echo "bad opt: $1" ; exit 1 ;;
        *) break ;;
    esac
done

create_tmpfile() {
    mktemp --tmpdir="${TMPDIR:-/tmp}" --suffix=".tmp" "$(basename "$0")"-XXXXXX
}

do_something() {
    echo "Doing something with: '$1'"

    if [[ -n "$do_something_delay" ]] ; then
        echo "Sleeping for $do_something_delay ..."
        sleep $do_something_delay
    fi

    if $sim_pipeerr ; then
        echo "Ooops, pipeline error in do_something!"
        : | false
    fi

    if $sim_earlyexit ; then
        echo "Oops, do_something called exit early!"
        exit 1
    fi
}

work_with_temp_file() {
    local tmpfile="$(create_tmpfile)"
    trap "rm -f '${tmpfile}'" RETURN EXIT

    # use $tmpfile
    do_something "${tmpfile}"

    # don't need to remember to rm $tmpfile at each repossible return point
    # don't need to worry about do_something failing or exiting early
}

work_with_temp_file