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semop KEY,OPSTRING

Calls the System V IPC function semop(2) for semaphore operations such as signalling and waiting. OPSTRING must be a packed array of semop structures. Each semop structure can be generated with pack("s!3", $semnum, $semop, $semflag). The length of OPSTRING implies the number of semaphore operations. Returns true if successful, false on error. As an example, the following code waits on semaphore $semnum of semaphore id $semid:

my $semop = pack("s!3", $semnum, -1, 0);
die "Semaphore trouble: $!\n" unless semop($semid, $semop);

To signal the semaphore, replace -1 with 1. See also "SysV IPC" in perlipc and the documentation for IPC::SysV and IPC::Semaphore.

Portability issues: "semop" in perlport.