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=`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 *************
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.
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