# semctl - perldoc - phpman

    semctl ID,SEMNUM,CMD,ARG
            Calls the System V IPC function [semctl(2)](https://www.chedong.com/phpMan.php/man/semctl/2/markdown). You'll probably have
            to say

                use [IPC::SysV](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASysV/markdown);

            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 with "pack("s!",(0)x$nsem)". See also "SysV IPC" in
            perlipc and the documentation for "[IPC::SysV](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASysV/markdown)" and
            "[IPC::Semaphore](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASemaphore/markdown)".

            Portability issues: "semctl" in perlport.