Shell Programming and Scripting

Hi,

Just wonder if there is a way to identify the PID of the killing process using trap.

Please let me know possible solution.

Code:

#!/bin/ksh

hello () {
print "in hello";
print "PID of process issued SIGNAL"; --> this is what i'm looking for. 
}

trap hello SIGKILL SIGTERM

while true
do
  print "in loop";
  sleep 1;
done

First note that you cannot trap a SIGKILL signal. If your process receives a SIGKILL, it will be terminated without a chance to execute any more instructions. (This is the case for any process; not just shell scripts.)

If you are writing a C program, and you use a signal catching function that gives you a siginfo_t structure when a signal is received and the signal received is of a few certain types and was sent under certain conditions, that C program can determine the process ID and user ID of the process that sent the signal. I don't know of any shell that catches this information and makes it available to code running as an action in a trap command when a shell script receives a signal.

I don't think you can do that easily in a shell script.

But if you control the killing process you can have it transfer its PID to the process that is to be killed, through a named pipe in /tmp for example:

Code:

#!/bin/ksh

hello () {
print "in hello";
read killproc < "$pipe"
print "PID of process that issued SIGNAL: $killproc"
exit
}

pipe=/tmp/killerproc.$$
mkfifo $pipe
trap "rm -f $pipe" EXIT
trap hello SIGKILL SIGTERM


while true
do
  print "in loop of process $$";
  sleep 1;
done

And then kill the process with something like this:

Code:

# killpid=<pid of process to be killed>
pipe=/tmp/killerproc.$killpid
kill "$killpid" ; echo $$ > $pipe

This would need to be refined, but you get the idea.

Thank You Don Cragun and Scrutinizer for your useful responses. I will try in one of this approach.