This is an OS-specific question. The usual answers are to leave a file with a process ID laying around and variations of that. If the PID is still active, then the process must be too. Or grunge through some kinds of process listing looking for the name.

Another answer is to open/lock a file -- if it fails (for a specific reason) then someone else has the file open and locked: your other instance.

One way I like to do it is to bind a specific network port on localhost. You don't actually have to listen to the port, just bind it. Only one "process" can bind a port at a time. If you try to bind and it's already bound, then there's already an instance of you running. (Note: pick a good out-of-the-way port number...) It's a portable technique and almost foolproof.

In reply to Re: Exec or system functions by clintp
in thread Exec or system functions by Anonymous Monk

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