i don't understand about trap and signals. why do i have to use it and how can i use it?

Hi.

Unix signal is a kind of event sent asynchronously to your program by other programs. trap allows you to declare signal handler. For example your script may create some temporary files which should be deleted when script exits. But if user press Ctrl+C, thus sending SIGINT signal to your program, the program exits immediately, leaving a mess of temporary files on the disk. To handle SIGINT signal:
Some signals, like USR1, USR2, are often used to reload configuration files without stopping the program.
Signals may be sent using the kill utility.

See man 1 kill, help trap, man -k kill for details.

Hope that helps.

thx a lot, i'll try to get into it.

i use trap to react when i send a signal INT to kill a process. the process can detect a signal, but it isn't stop.

i use sleep command in the process that i want to kill. anyone knows what's going on?

Main Script
===================================
#!/bin/bash
echo $$

function initKill() {
echo "Receive SIGINT"
kill -9 $$
exit 1
}

trap initKill SIGINT

sleep 60
===================================

Kill Script
===================================
#!/bin/bash

kill -SIGINT $1
===================================

Hi.

Here is a quote from man bash:
Because SIGINT by default causes process to exit, you may send it to whole process group. It will cause pause 60 to exit and then the signal handler of your script will be executed. To send a signal to process group, negate the pid (add minus sign) in the kill command line.

thank you a lot ^^