Re: `wait -n` returns 127 when it shouldn't

[Chet Ramey]

On 5/16/23 1:35 PM, Aleksey Covacevice wrote:

> Bash Version: 5.1
> Patch Level: 16
> Release Status: release
>
> Description:
> `wait -n` sometimes returns with status code 127 even though there are
> unwaited-for children.

There are not. That's why `wait -n' returns 127.

> Repeat-By:
> The following script does finish after a while:
>
> waitjobs() {
>      local status=0
>      while true; do
>      local code=0; wait -n || code=$?
>          ((code == 127)) && break
>          ((!code)) || status=$code
>      done
>      return $status
> }
>
> # Eventually finishes:
> while true; do (
>      true &
>      false &
>      waitjobs
> ) && break; done

It's possible for the shell to reap both background jobs before `wait -n'
is called. The underlying function returns < 0 when there aren't any
unwaited-for jobs, which the wait builtin translates to 127.

--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/