Re: [PLUG] How to find parent in the shell?

["Michael C. Toren" <mct@toren.net>]

On Tue, Jan 06, 2004 at 03:11:11PM -0500, Stephen Gran wrote:
> > I don't see how testing to see if your parent process is init will give
> > you any insight into weather or not your script is being executed at boot
> > time or not, unfortunately.  What if a user types "exec
> > /etc/init.d/whatever" from a console login shell?
> 
> Well, that would actually be fine.  The only thing I am trying to do is
> have the script run at boot, but not be rerun on upgrade.

If you don't mind being dependent on /proc and bash, perhaps:

	#!/bin/bash

	set -e
	pid=$$

	while [ $pid -gt 1 ]
	do
	    ppid=$(awk '/^PPid:/ {print $2}' /proc/$pid/status)
	    tr '\0' ' ' < /proc/$pid/cmdline | awk '{print $1}' | \
		awk -F/ '{print $NF}' | grep -q ^dpkg && exit 1
	    pid=$ppid
	done

The above script traces it's lineage back to init, and if it finds an
ancestor named "dpkg*", it dies with an exit status of 1.  Otherwise,
it exits cleanly.

-mct
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