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List:       bash-bug
Subject:    Re: Process Substitution subshell inherits the desire to print its times if it contains explicit exi
From:       Chet Ramey <chet.ramey () case ! edu>
Date:       2018-04-04 18:36:02
Message-ID: ef698caa-0717-25bf-be1a-cfa0b8799e19 () case ! edu
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On 4/4/18 4:21 AM, Basin Ilya wrote:
> Hi.
> 
> In an attempt to capture the output of 'time' I used the process substitution and \
> noticed that the subshell also prints its times. Actually I this happens when I \
> redirect any fd, not just stderr.

It's an interaction between command timing and the `exit' builtin wanting
to make sure it does things like run any exit trap. The file descriptor
manipulation doesn't matter; it's the process substitution subshell
creation that does it. A command like `cat <( echo procsub ; exit 0)'
would work just as well. I'll take a look at the best way to fix it.

> 
> #!/bin/bash
> 
> time {
> sleep 0.25
> exec 6> >(
> sed 's/^/captured: /'
> exit 0
> )
> }
> 
> # close write side of the pipe and wait for reader
> exec 6>&-
> wait $!
> 
> 

> Earlier bash versions just print: wait: pid 28717 is not a child of this shell

Bash-4.4 allows wait to reap the last process substitution created, since
it sets $!.

Chet
-- 
``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/


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