---
name: "IPC::SysV"
section: "3p"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["openbsd"]
url: "https://new.carta.tech/IPC::SysV"
---

# IPC::SysV(3p)

System V IPC constants and system calls

## NAME

IPC::SysV - System V IPC constants and system calls

## SYNOPSIS

```
  use IPC::SysV qw(IPC_STAT IPC_PRIVATE);
```

## DESCRIPTION

`"IPC::SysV"` 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)](/ftok/3.md).

  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)](/shmat/2.md).

  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)](/shmdt/2.md).

- 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, IPC::Semaphore, IPC::SharedMem, [**ftok**(3)](/ftok/3.md), [**shmat**(2)](/shmat/2.md), [**shmdt**(2)](/shmdt/2.md)

## 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.