Date: Wed, 07 Feb 2007 16:07:23 -0600 From: Derek Ragona <derek@computinginnovations.com> To: "Aitor San Juan" <asanjuan@bolsabilbao.es>, <freebsd-questions@freebsd.org> Subject: Re: Trapping signal from shell script... doesn't seem to work? Message-ID: <6.0.0.22.2.20070207160529.027c8ab0@mail.computinginnovations.com> In-Reply-To: <D44BEB355E6EC14C9B825F8C956E12E1E4C1@BB06.bolsabilbao.loca l> References: <6FA4E8E8A0FAD64F9AF5A1F0FDB8C6EE1211@BB06.bolsabilbao.local> <D44BEB355E6EC14C9B825F8C956E12E1E4C1@BB06.bolsabilbao.local>
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I believe what you are seeing is the login shell you are running holding=20
back the signal as it first traps the signals. You should try running the=
=20
script non-interactively from cron or nohup.
-Derek
At 09:18 AM 2/7/2007, Aitor San Juan wrote:
>Hi list!
>
>I have written a Bourne shell script. This shell script invokes a
>program written in the C language.
>
>Below is basically the shell script source code. As you can see,
>the C program is not invoked in the background, but in the
>foreground, so the shell script doesn't finish until the C program
>has finished.
>
>I want the shell script to trap TERM or INT signals, so when any
>of these are raised, the shell script will try to send SIGTERM to
>the program "myprog":
>
>user1:/usr/home/user1$ ps -ax | grep -v grep | grep myprog
> PID TT STAT TIME COMMAND
>22406 p0 I+ 0:00.01 /bin/sh ../cronjobs/myshell.sh
>22449 p0 I+ 0:00.00 /usr/home/user1/myprog -d
>
>user1:/usr/home/user1$ kill -TERM 22406
>
>user1:/usr/home/user1$ ps -ax | grep -v grep | grep myprog
> PID TT STAT TIME COMMAND
>22406 p0 S+ 0:00.01 /bin/sh ../cronjobs/myshell.sh
>22449 p0 I+ 0:00.00 /usr/home/user1/myprog -d
>
>I notice the change in state of the shell script process from I+
>to S+, but nothing else happens. The shell script seems to remain
>in execution. However as soons as I press Ctrl-C at the terminal
>where I invoked the shell script, it indeed receives the Ctrl-C,
>but "myprog" receives it first so when the function "trap_handler"
>executes, there is no "myprog" process in memory.
>
>My question: Can anybody tell me what happens and/or what am I
>doing wrong? Why must I press Ctrl-C to force the shell script to
>finally receive the TERM signal when I executed the kill command
>from another session? What is this apparent delay due to?
>
>Thanks in advance.
>
>#------------------ SHELL SCRIPT BEGIN ------------------
>#!/bin/sh
>#
>trap_handler() {
> echo "*** SYSTEM SIGNAL RECEIVED ***"
> echo "$1 caught. Ending..."
> pid=3D`find_myprog's_PID`
> kill -TERM $pid
> exit 1
>}
>
>trap 'trap_handler SIGINT' INT
>trap 'trap_handler SIGTERM' TERM
>
>/usr/home/user1/myprog -d
>#------------------ SHELL SCRIPT END ------------------
>
>
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