Why I am not getting signal SIGKILL on kill -9 command in bash?

Question

In bash script I handle different signal as follows:

#!/bin/bash

sighdl () 
{
  echo \"signal caught\"
  #do something
  exit 0
}

trap sighdl SIGKILL SIGINT SI         


        

Answer 1

You cannot do that. Yes 9 is SIGKILL and Unix system by design doesn't allow any script/program to trap SIGKILL due to security reasons. Otherwise any script can trap & ignore SIGKILL which will make impossible to terminate that script by OS.