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From: "" <kfm@plushkava.net>
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Subject: Re: process substitution error handling
Date: Thu, 6 Aug 2020 17:36:35 +0100
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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