Thanks for the suggestion. I have already tried an exclusive creation (IPC_CREAT | IPC_EXCL) which I understand is what you're suggesting. I hit the same issue...the files arrive too closely together that neither create process detects that the semaphore has already been created so they both create successfully!

In reply to Re^2: Semaphore puzzle by jerryhone
in thread Semaphore puzzle by jerryhone

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