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

$ bash 2013-10-03-lhunath-bashlib
should pass
bash_lineno x o o o o o : printf %s\n "$((! BASH_LINENO))"
bash_return o o o o o o : (return 2>/dev/null); echo $?

---

should fail
bash_lineno x x x : printf %s\n "$((! BASH_LINENO))"
bash_return x x x : (return 2>/dev/null); echo $?

just an fyi, i had my own technique for this that i recently switched to (return 2>/dev/null) thanks to this.

adding this

printf '%s\n' \
  '[[ ${BASH_SOURCE[0]} != $0 ]]; echo $?' \
  > bash_source

i got

should pass
bash_lineno x o o o o o : printf %s\\n "$((! BASH_LINENO))"
bash_return o o o o o o : (return 2>/dev/null); echo $?
bash_source o o o o o o : [[ ${BASH_SOURCE[0]} != $0 ]]; echo $?
--------------------------------------------------------------------------------
should fail
bash_lineno x x x : printf %s\\n "$((! BASH_LINENO))"
bash_return x x x : (return 2>/dev/null); echo $?
bash_source x o x : [[ ${BASH_SOURCE[0]} != $0 ]]; echo $?

it doesn't fail when it should... (return 2>/dev/null) seems to be the cleanest approach.

@bahamas10 Nice! I didn't see your reply in time. It's an ugly trick but it seems to work. If you find more situations where it could fail please tell me so :)

You need to write 'return 0' rather than just return, or else

false; source bash_return

prints 1.

And, when using trap 'rm -rf "$tempdir"' EXIT, always assume that the caller did export tempdir=/, and that you get a signal between the trap and the mktemp. (Actually, that's hard to arrange). So, either unset tempdir, or put the trap after the mktemp call.

@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 :-)