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IPC::Semaphore - SysV Semaphore IPC object class


  2. use IPC::Semaphore;
  3. $sem = IPC::Semaphore->new(IPC_PRIVATE, 10, S_IRUSR | S_IWUSR | IPC_CREAT);
  4. $sem->setall( (0) x 10);
  5. @sem = $sem->getall;
  6. $ncnt = $sem->getncnt;
  7. $zcnt = $sem->getzcnt;
  8. $ds = $sem->stat;
  9. $sem->remove;


A class providing an object based interface to SysV IPC semaphores.


  • new ( KEY , NSEMS , FLAGS )

    Create a new semaphore set associated with KEY . NSEMS is the number of semaphores in the set. A new set is created if

    • KEY is equal to IPC_PRIVATE

    • KEY does not already have a semaphore identifier associated with it, and FLAGS & IPC_CREAT is true.

    On creation of a new semaphore set FLAGS is used to set the permissions. Be careful not to set any flags that the Sys V IPC implementation does not allow: in some systems setting execute bits makes the operations fail.

  • getall

    Returns the values of the semaphore set as an array.

  • getncnt ( SEM )

    Returns the number of processes waiting for the semaphore SEM to become greater than its current value

  • getpid ( SEM )

    Returns the process id of the last process that performed an operation on the semaphore SEM .

  • getval ( SEM )

    Returns the current value of the semaphore SEM .

  • getzcnt ( SEM )

    Returns the number of processes waiting for the semaphore SEM to become zero.

  • id

    Returns the system identifier for the semaphore set.

  • op ( OPLIST )

    OPLIST is a list of operations to pass to semop. OPLIST is a concatenation of smaller lists, each which has three values. The first is the semaphore number, the second is the operation and the last is a flags value. See semop for more details. For example

    1. $sem->op(
    2. 0, -1, IPC_NOWAIT,
    3. 1, 1, IPC_NOWAIT
    4. );
  • remove

    Remove and destroy the semaphore set from the system.

  • set ( STAT )
  • set ( NAME => VALUE [, NAME => VALUE ...] )

    set will set the following values of the stat structure associated with the semaphore set.

    1. uid
    2. gid
    3. mode (only the permission bits)

    set accepts either a stat object, as returned by the stat method, or a list of name-value pairs.

  • setall ( VALUES )

    Sets all values in the semaphore set to those given on the VALUES list. VALUES must contain the correct number of values.

  • setval ( N , VALUE )

    Set the N th value in the semaphore set to VALUE

  • stat

    Returns an object of type IPC::Semaphore::stat which is a sub-class of Class::Struct . It provides the following fields. For a description of these fields see your system documentation.

    1. uid
    2. gid
    3. cuid
    4. cgid
    5. mode
    6. ctime
    7. otime
    8. nsems


IPC::SysV, Class::Struct, semget, semctl, semop


Graham Barr <>, Marcus Holland-Moritz <>


Version 2.x, Copyright (C) 2007, 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.