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#!/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
@dualbus

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@dualbus dualbus commented Oct 3, 2013

$ 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 $?

@bahamas10

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@bahamas10 bahamas10 commented Oct 17, 2013

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.

@dualbus

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@dualbus dualbus commented Dec 20, 2013

@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 :)

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@ejhuff ejhuff commented Oct 7, 2014

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.

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@dualbus dualbus commented Apr 1, 2015

@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 :-)

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