Date: Thu, 24 Mar 2022 18:13:01 +0100 From: Ganael Laplanche <ganael.laplanche@martymac.org> To: freebsd-hackers@freebsd.org Subject: Our /bin/sh and process group IDs Message-ID: <48e49ad0-a12a-d10b-5867-da9736c6c1fd@martymac.org>
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Hello,
I am trying to fork a sub-shell with its own process group id through a
function that must itself be executed in the background.
It should work with the following code:
#----
#!/bin/sh
# Parent shell IDs
ps -o pid,ppid,pgid,comm -p $$
test_func () {
set -m
{ /bin/sh -c 'sleep 1' ; } &
# Forked shell IDs (pgid should be different from parent,
# but it is not)
ps -o pid,ppid,pgid,comm -p $!
}
# The following does not work:
test_func &
# ...but it works when function is not executed in the background:
#test_func
sleep 2
exit 0
#----
Unfortunately, with our /bin/sh, the sleeping process gets the *same*
process group ID as its parent.
I've tested several shell implementations; it works with :
/usr/local/bin/bash --posix 'test.sh' # from bash-5.1.16
/usr/local/bin/zsh --emulate sh 'test.sh' # from zsh-5.8.1
/usr/local/bin/ksh93 'test.sh' # from ksh93-devel-2020.06.30
/usr/local/bin/mksh 'test.sh' # from mksh-59c
/usr/local/bin/ksh 'test.sh' # from pdksh-5.2.14p2_6
but not with :
/bin/sh 'test.sh' # on 13.0-RELEASE-p8
/usr/local/bin/dash 'test.sh' # from dash-0.5.11.5
am I missing something ?
Any help welcome :)
Best regards,
--
Ganael LAPLANCHE <ganael.laplanche@martymac.org>
http://www.martymac.org | http://contribs.martymac.org
FreeBSD: martymac <martymac@FreeBSD.org>, http://www.FreeBSD.org
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