There are many solutions to that problem. The simplest is that if the processes aren't supposed to run at once, don't start them in parallel! Start one, let it finish, start the next, let it finish, etc.

Otherwise, I'd use a lockfile, or a locking mechanism in a database. You say flock() doesn't work, but I fail to understand why. Since only one process at a time can have an exclusive lock at one time, this seems like an ideal mechanism.

Abigail

In reply to Re: Logical Conundrum by Abigail-II
in thread Logical Conundrum by mcogan1966

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