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IPC::SharedMem.3perl

NAME

IPC::SharedMem - SysV Shared Memory IPC object class

SYNOPSIS

     use IPC::SysV qw(IPC_PRIVATE S_IRUSR S_IWUSR);
     use IPC::SharedMem;
 
     $shm = IPC::SharedMem->new(IPC_PRIVATE, 8, S_IRWXU);
 
     $shm->write(pack("S", 4711), 2, 2);
 
     $data = $shm->read(0, 2);
 
     $ds = $shm->stat;
 
     $shm->remove;
 
 

DESCRIPTION

A class providing an object based interface to SysV IPC shared memory.

METHODS

new ( KEY , SIZE , FLAGS )

Creates a new shared memory segment associated with "KEY". A new segment is created if

•

"KEY" is equal to "IPC_PRIVATE"

•

"KEY" does not already have a shared memory segment associated with it, and "FLAGS & IPC_CREAT" is true.

On creation of a new shared memory segment "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.

id

Returns the shared memory identifier.

read ( POS, SIZE )

Read "SIZE" bytes from the shared memory segment at "POS". Returns the string read, or "undef" if there was an error. The return value becomes tainted. See shmread.

write ( STRING, POS, SIZE )

Write "SIZE" bytes to the shared memory segment at "POS". Returns true if successful, or false if there is an error. See shmwrite.

remove

Remove the shared memory segment from the system or mark it as removed as long as any processes are still attached to it.

is_removed

Returns true if the shared memory segment has been removed or marked for removal.

stat

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

     uid
     gid
     cuid
     cgid
     mode
     segsz
     lpid
     cpid
     nattach
     atime
     dtime
     ctime
 
 

attach ( [FLAG] )

Permanently attach to the shared memory segment. When a "IPC::SharedMem" object is attached, it will use memread and memwrite instead of shmread and shmwrite for accessing the shared memory segment. Returns true if successful, or false on error. See shmat.

detach

Detach from the shared memory segment that previously has been attached to. Returns true if successful, or false on error. See shmdt.

addr

Returns the address of the shared memory that has been attached to in a format suitable for use with "pack('P')". Returns "undef" if the shared memory has not been attached.

SEE ALSO

IPC::SysV, Class::Struct

AUTHORS

Marcus Holland-Moritz <mhx@cpan.org>

COPYRIGHT

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.