Could any one explain what is the meaning of exit 4 in UNIX shell script

The exit command sets the exit code in a calling shell script. Based on what happens in the child script, you can take some action in the parent. Here is an example where parent.ss calls child.ss. #!/bin/ksh # parent.ss call child and look at exit code ./child.ss # execute the child echo $? # should be 4 # end parrent.ss # child.ss exit set to 4 exit 4 # end child.ss There is a limit to the exit value. It's probably system dependent, but as I remember it's around 256. If it matters, you'll have to check.