IPC::Semaphore

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• NAME
• SYNOPSIS
• DESCRIPTION
• METHODS
• SEE ALSO
• AUTHOR
• COPYRIGHT

NAME

IPC::Semaphore - SysV Semaphore IPC object class

SYNOPSIS

    use IPC::SysV qw(IPC_PRIVATE S_IRUSR S_IWUSR IPC_CREAT);
    use IPC::Semaphore;

    $sem = new IPC::Semaphore(IPC_PRIVATE, 10, S_IRUSR | S_IWUSR | IPC_CREAT);

    $sem->setall( (0) x 10);

    @sem = $sem->getall;

    $ncnt = $sem->getncnt;

    $zcnt = $sem->getzcnt;

    $ds = $sem->stat;

    $sem->remove;

DESCRIPTION

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

METHODS

• 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 <i>FLAGS</i> & 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

      $sem->op(
  	0, -1, IPC_NOWAIT,
  	1,  1, IPC_NOWAIT
      );

• 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.

      uid
      gid
      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.

      uid
      gid
      cuid
      cgid
      mode
      ctime
      otime
      nsems

SEE ALSO

IPC::SysV Class::Struct semget semctl semop

AUTHOR

Graham Barr <gbarr@pobox.com>

COPYRIGHT

Copyright (c) 1997 Graham Barr. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.