Date: Wed, 7 Feb 2007 16:18:53 +0100 From: "Aitor San Juan" <asanjuan@bolsabilbao.es> To: <freebsd-questions@freebsd.org> Subject: Trapping signal from shell script... doesn't seem to work? Message-ID: <D44BEB355E6EC14C9B825F8C956E12E1E4C1@BB06.bolsabilbao.local> In-Reply-To: <6FA4E8E8A0FAD64F9AF5A1F0FDB8C6EE1211@BB06.bolsabilbao.local>
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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 ------------------
************ LEGEZKO OHARRA / AVISO LEGAL / LEGAL ADVICE *************=20
Mezu honek isilpeko informazioa gorde dezake, edo jabea duena, edota =
legez babestuta dagoena. Zuri zuzendua ez bada, bidali duenari esan eta =
ezabatu, inori berbidali edo gorde gabe, legeak debekatzen duelako =
mezuak erabiltzea baimenik gabe.=20
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