#!/bin/bash
#
# Usage:
#
#       finally <eval-string> <cmd> [args...]
#
# What it does:
#
#       (1) First, the <cmd> is executed with its arguments if any.
#
#       (2) Then <eval-string> is executed as it would be by eval in
#           the most global scope of the shell.  (It is actually sent to
#           the bash prompt's standard input as a list of quoted words.)
#
# Reason to exist:
#
#       If execution of <cmd> is interrupted by signal, the
#       <eval-string> will still run.

finally()
{
        exec \
                {FINALLY_0}<&0 \
                {FINALLY_1}>&1 \
                {FINALLY_2}>&2 \
                0< <(finally_unwind "$1") \
                &> /dev/null # silence prompt
                # note that finally_unwind still has un-redirected
                # stdin/stderr
        {
                "${@:2}"
        } <&$FINALLY_0 >&$FINALLY_1 2>&$FINALLY_2
}

finally_unwind()
{
        case $# in
                0 )
                        exec \
                                0<&$FINALLY_0 \
                                1>&$FINALLY_1 \
                                2>&$FINALLY_2 \
                                {FINALLY_0}<&- \
                                {FINALLY_1}>&- \
                                {FINALLY_2}>&-
                ;;
                1 )
                        echo "history -d -1; finally_unwind; $1"
                ;;
        esac
}