semctl function

SysV semaphore control operations Calls the System V IPC function semctl(). You'll probably have to say 

    use IPC::SysV;

first to get the correct constant definitions. If CMD is IPC_STAT or GETALL, then ARG must be a variable which will hold the returned semid_ds structure or semaphore value array. Returns like ioctl(): the undefined value for error, ``0 but true'' for zero, or the actual return value otherwise. See also IPC::SysV and IPC::Semaphore documentation.