semctl

See the current Perl documentation for semctl.

Here is our local, out-dated (pre-5.6) version:

semctl - SysV semaphore control operations

semctl ID,SEMNUM,CMD,ARG

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.