# phpman > info > IPC::SysV

IPC::[SysV(3perl)](https://www.chedong.com/phpMan.php/man/SysV/3perl/markdown)       Perl Programmers Reference Guide       IPC::[SysV(3perl)](https://www.chedong.com/phpMan.php/man/SysV/3perl/markdown)

NAME
       [IPC::SysV](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASysV/markdown) - System V IPC constants and system calls

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

DESCRIPTION
       "[IPC::SysV](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASysV/markdown)" defines and conditionally exports all the constants defined
       in your system include files which are needed by the SysV IPC calls.
       Common ones include

         IPC_CREAT IPC_EXCL IPC_NOWAIT IPC_PRIVATE IPC_RMID IPC_SET IPC_STAT
         GETVAL SETVAL GETPID GETNCNT GETZCNT GETALL SETALL
         SEM_A SEM_R SEM_UNDO
         SHM_RDONLY SHM_RND SHMLBA

       and auxiliary ones

         S_IRUSR S_IWUSR S_IRWXU
         S_IRGRP S_IWGRP S_IRWXG
         S_IROTH S_IWOTH S_IRWXO

       but your system might have more.

       ftok( PATH )
       ftok( PATH, ID )
           Return a key based on PATH and ID, which can be used as a key for
           "msgget", "semget" and "shmget". See [ftok(3)](https://www.chedong.com/phpMan.php/man/ftok/3/markdown).

           If ID is omitted, it defaults to 1. If a single character is given
           for ID, the numeric value of that character is used.

       shmat( ID, ADDR, FLAG )
           Attach the shared memory segment identified by ID to the address
           space of the calling process. See [shmat(2)](https://www.chedong.com/phpMan.php/man/shmat/2/markdown).

           ADDR should be "undef" unless you really know what you're doing.

       shmdt( ADDR )
           Detach the shared memory segment located at the address specified
           by ADDR from the address space of the calling process. See
           [shmdt(2)](https://www.chedong.com/phpMan.php/man/shmdt/2/markdown).

       memread( ADDR, VAR, POS, SIZE )
           Reads SIZE bytes from a memory segment at ADDR starting at position
           POS.  VAR must be a variable that will hold the data read. Returns
           true if successful, or false if there is an error. memread() taints
           the variable.

       memwrite( ADDR, STRING, POS, SIZE )
           Writes SIZE bytes from STRING to a memory segment at ADDR starting
           at position POS. If STRING is too long, only SIZE bytes are used;
           if STRING is too short, nulls are written to fill out SIZE bytes.
           Returns true if successful, or false if there is an error.

SEE ALSO
       [IPC::Msg](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3AMsg/markdown), [IPC::Semaphore](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASemaphore/markdown), [IPC::SharedMem](https://www.chedong.com/phpMan.php/perldoc/IPC%3A%3ASharedMem/markdown), [ftok(3)](https://www.chedong.com/phpMan.php/man/ftok/3/markdown), [shmat(2)](https://www.chedong.com/phpMan.php/man/shmat/2/markdown), [shmdt(2)](https://www.chedong.com/phpMan.php/man/shmdt/2/markdown)

AUTHORS
       Graham Barr <<gbarr@pobox.com>>, Jarkko Hietaniemi <<jhi@iki.fi>>, Marcus
       Holland-Moritz <<mhx@cpan.org>>

COPYRIGHT
       Version 2.x, Copyright (C) 2007-2013, Marcus Holland-Moritz.

       Version 1.x, Copyright (c) 1997, Graham Barr.

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.

perl v5.34.0                      2025-07-25                  IPC::[SysV(3perl)](https://www.chedong.com/phpMan.php/man/SysV/3perl/markdown)