Re: process substitution error handling

On 06/08/2020 17:21, Eli Schwartz wrote:
> On 8/6/20 11:31 AM, Jason A. Donenfeld wrote:
> > That doesn't always work:
> >
> > set -e
> > while read -r line; do
> >         echo "$line" &
> > done < <(echo 1; sleep 1; echo 2; sleep 1; exit 77)
> > sleep 1
> > wait $!
> > echo done

I wonder why wait $! doesn't do the job here.

> So instead of your contrived case, write it properly. Check the process
> substitution first, and make sure as a bonus you don't run anything if
> if it failed:
>
> set -e
> mapfile -t lines < <(echo 1; sleep 1; echo 2; sleep 1; exit 77)
> wait $!
>
> for line in "${lines[@]}"; do
>         echo "$line" &
> sleep 1
> wait $!
> echo done

As Jason appears set on using "set -e -o pipefail", here is another 
approach that may be more to his taste:

set -e -o pipefail
{ echo 1; sleep 1; echo 2; sleep 1; exit 77; } | while read -r line; do
        echo "$line" &
done
sleep 1
echo done

Of course, the loop will be executed in a subshell, but that can be 
averted by shopt -s lastpipe.

--
Kerin Millar