SysV semaphore operations

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• semop KEY,OPSTRING

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

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

  To signal the semaphore, replace -1 with 1. See alsoSysV IPC in perlipc, IPC::SysV, and IPC::SysV::Semaphoredocumentation.

  Portability issues: semop in perlport.