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Re: forked before bash subshell


From: Chet Ramey
Subject: Re: forked before bash subshell
Date: Sat, 15 Oct 2016 22:03:08 -0400
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.4.0

On 10/11/16 10:14 PM, address@hidden wrote:
> 1. the script to reproduce
> bash-4.4$ cat t.sh 
> (cd /tmp && sleep 20) &
> 
> echo "end"
> 
> 
> 2. run it
> bash-4.4$ bash t.sh 
> end
> 
> 3. script end, but there is a new forked script.
> bash-4.4$ ps -ef | grep t.sh
>   501 50268     1   0 10:09AM ttys015    0:00.00 bash t.sh
>   501 50275 50181   0 10:10AM ttys015    0:00.00 grep t.sh
> 
> 
> 
> question:
> when using sh -> dash, It will not fork before subshell, what's the different?
> 
> why bash bahavior like this? is that a bug?

It's not a bug; it's an opportunity for optimization.  It's like this
because it hasn't come up as a performance problem.  I'll take a look
at it.  There are probably several opportunities like this.

Chet

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



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