Checking if script is running

Question

I need to find out if a script is not running. When I do the "ps -afe | grep nameOfScript" it gives me no output if the "nameOfScript" is not running. How can I get an output or get a message to say "nameOfScript" is not running. Is there some sort of grep or something I can use to get this to work

Answer 1

The fact that nothing comes back means the script isn't running - usually. Your script logic is what takes care of saying "Thar ain't nuttin' here honey".
But using your ps -afe example you need to make sure you only get back instances of the running script. With your example, if I run "vi nameOfScript", your ps -afe command will show my vi command in the list and your script logic may incorrect assumely the script is running when it really isn't.
You need to make your logic that looks for the script running a bit more specific. The way you run the script will dictate how it shows up in a ps listing. Like this:
cd /path/to/script
./nameOfScript &
In a "ps -afe", this will show up as the string:
/bin/ksh ./nameOfScript
But if you execute it with the full path:
/path/to/script/nameOfScript &
It will show up as:
/bin/ksh /path/to/script/nameOfScript
So you can see, your logic has to handle all fo these cases. From practical experience, its usually better to have the script create a temporary PID file somewhere. When the script dies, it automagically deletes this file or something. When you check to see if the script is running, you read contents of PID file (assuming it exists), and check a ps listing to see if PID 1234 (or whatever the PID is) is really your script. Kinda a pain in the arse I know but this is usually the best way to handle this.
Probably more then you asked for ;>