UNIX for Advanced & Expert Users

I have a script, myscript.pl

I want to set the script to exit if it is already running.

At the moment I am using soft stop.
eg:
if -e dummy file then exit
else create a dummy file

Is there any other better way to perform this?

Maybe

Code:

ps -ef | egrep 'myscript.pl'

The create a single file does have the advantage of simplicity, and with daemons has the dual purpose of being used to contain the pid of the running instance. Take care to delete this file when your process terminates using atexit/trap or equivalent, and obviously requires a standard place to hold the file which is writeable by the process owner.

The "ps" approach can also be used but you need to take care that you are not picking up some other process which either has that name within another string, is the process which is doing the search, or is part of a list of arguments or is yourself.

or alternatively you might want to look into 'fuser' (or 'lsof').
executing 'fuser /path/to/myscript.pl' will give you a list of the process PIDs "using" a file.
Obviously having more than 1 PID means there's another instance of a script running.

Exactly!
Adding to that,

once the pid is written to that file, revoke the write permission on the file and just make sure only read permission is available.

This is just a way to prevent accidental overwriting / deleting of the pid file

to this,
ps -fu $USERNAME would do