Check whether a process running

[guidance]

I use exec() to launch a program(process). I want only one instance to run at the same time while several clients are visiting the same page, the following ones must wait until the first instance is closed. How can I do that? My understanding for best solution is to check the process list whether this program is already running, but I don't know how to check this in PHP under Win2000+Apache2?

[mrhappiness]

why not creating a semaphore using php?

[LordShryku]

PHP can't acess Window's internal process list(Reason #3,468 that Linux is superior), but you can team with something like process viewer, which has a command line interface, and run exec to check it.