semctl
- semctl ID,SEMNUM,CMD,ARG
Calls the System V IPC function
semctl. You'll probably have to sayuse IPC::SysV;
first to get the correct constant definitions. If CMD is IPC_STAT or GETALL, then ARG must be a variable that 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. The ARG must consist of a vector of native short integers, which may be created withpack("s!",(0)x$nsem). See also "SysV IPC" in perlipc,IPC::SysV,IPC::Semaphoredocumentation.

