2013-10-03-lhunath-bashlib

#!/bin/bash

trap 'rm -rf "$tempdir"' EXIT
tempdir=$(mktemp -d)
cd "$tempdir" || exit 1

printf '%s\n' \
  '(return 2>/dev/null); echo $?' \
  > bash_return

printf '%s\n' \
  'printf %s\\n "$((! BASH_LINENO))"' \
  > bash_lineno


printf '%s\n' 'should pass'
for approach in bash_{lineno,return}; do
  printf '%s ' "$approach"
  {
    bash -c ". $approach"
    bash -s <<< ". $approach"
    printf '. %s\n' "$approach" > "$approach"_test;
    chmod +x "$approach"_test;
    ./"$approach"_test;
    bash "$approach"_test;
    . "$approach"_test;
    . "$approach";
  } | tr '\n01' ' ox'
  printf ': %s\n' "$(< "$approach")"
done
printf '%.s-' {0..79}; printf \\n

printf '%s\n' 'should fail'
for approach in bash_{lineno,return}; do
  printf '%s ' "$approach"
  {
    bash "$approach"
    bash -s < "$approach"
    eval "$(<"$approach")"
  } | tr '\n01' ' ox'
  printf ': %s\n' "$(< "$approach")"
done

@ejhuff Wow, this thing doesn't notify me. I agree with your points. Specially the second, I started doing: unset var; trap ' uses var ' FOO; var=... for this precisely, but I guess that was before I wrote this :-)