Re: return exit code in EXIT trap

[Robert E. Griffith]

> On 8/6/22 14:44, Robert Elz wrote:
> ... bash allows a return in the trap string (not in a function called in that 
> string) if the
> trap occurs while executing a function (then the return applies to that 
> function). ...
Yes! that is what I was missing.  Years ago when I wrote my debugger, I 
must have come across this and through trail and error I settled on 
ending the DEBUG trap with 'setExitCode $action' (where .. setExitCode() 
{ return $?; })

Even though I knew that bash did not push anything on the stack when it 
called a trap script I always thought there must be some notion of 
entering into and returning from a trap script but no, return in a trap 
function is just like inserting a return in the interrupted script, 
where ever its at!

Here is a test script that I just used to understand and confirm for 
myself whats going on and that also illustrates the B behavior....

   bash5.0.16$ cat bin/test.sh
   #!/usr/bin/env bash
   function setExitCode() { return $1; }
   function f1() {
        sleep 2
        echo "f1 -- woke, no signal -- ending normally"
        return 101
   }
   function childFn() {
        trap 'echo "SIG: signal received -- ending f1 with last code 202 -> return   
"; setExitCode 202; return '    SIGUSR1
        trap 'echo "SIG: signal received -- ending f1 with last code 202 -> return 
\$?"; setExitCode 202; return $?'  SIGUSR2
        f1
        echo "f1 returned $?"
   }
   childFn &
   child="$!"
   sleep 1
   case $1 in
        1) echo "main: sending USR1"; kill -SIGUSR1 $child ;;
        2) echo "main: sending USR2"; kill -SIGUSR2 $child ;;
        *) echo "main: twiddling thumbs" ;;
   esac
   wait
   echo

   bash5.0.16$ bin/test.sh
   main: twiddling thumbs
   f1 -- woke, no signal -- ending normally
   f1 returned 101

   bash5.0.16$ bin/test.sh 1
   main: sending USR1
   SIG: signal received -- ending f1 with last code 202 -> return
   f1 returned 0

   bash5.0.16$ bin/test.sh 2
   main: sending USR2
   SIG: signal received -- ending f1 with last code 202 -> return $?
   f1 returned 202

   bash5.0.16$

The second run (that causes USR1 to interrupt f1) shows the B behavior 
compared to the third (USR2) that shows the more correct A behavior by 
explicitly using 'return $?'

--BobG