semop KEY,OPSTRING
Calls the System V IPC function semop to perform semaphore operations
such as signaling and waiting. OPSTRING must be a packed array of
semop structures. Each semop structure can be generated with
pack("sss", $semnum, $semop, $semflag). The number of semaphore
operations is implied by the length of OPSTRING. Returns TRUE if
successful, or FALSE if there is an error. As an example, the
following code waits on semaphore $semnum of semaphore id $semid:
$semop = pack("sss", $semnum, ™1, 0);
die "Semaphore trouble: $!\n" unless semop($semid, $semop);
To signal the semaphore, replace "™1" with "1".
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