/ 
SysV-SharedMem-0.003
River stage zero No dependents
/ SysV::SharedMem

NAME

SysV::SharedMem - SysV Shared memory made easy

VERSION

Version 0.003

SYNOPSIS

use SysV::SharedMem;

shared_open my $mem, '/path', '+>', size => 4096;
vec($mem, 1, 16) = 34567;
substr $mem, 45, 11, 'Hello World';

This module maps shared memory into a variable that can be read just like any other variable, and it can be written to using standard Perl techniques such as regexps and substr, as long as they don't change the length of the variable.

METHODS

shared_open($var, $filename, $mode, %options)

Open a shared memory object named $filename and attach it to $var. $filename must be the path to an existing file or undef, in which case the key option is used. $mode determines the read/write mode. It works the same as in open.

Beyond that it can take a number of optional named arguments:

  • size

    This determines the size of the map. Must be set if a new shared memory object is being created.

  • perms

    This determines the permissions with which the file is created (if $mode is '+>'). Default is 0700.

  • offset

    This determines the offset in the file that is mapped. Default is 0.

  • key

    If $filename is undefined this parameter is used as the key to lookup the shared memory segment. It defaults to IPC_PRIVATE, which causes a new, anonymous shared memory segment to be created.

  • id

    The project id, used to ensure the key generated from the filename is unique. Only the lower 8 bits are significant and may not be zero. Defaults to 1.

shared_remove($var)

Marks a memory object to be removed. Shared memory has kernel persisence so it has to be explicitly disposed of. One can still use the object after marking it for removal.

shared_stat($var)

Retrieve the properties of the shared memory object. It returns a hashref with these members:

  • uid

    Owner's user ID

  • gid

    Owner's group ID

  • cuid

    Creator's user ID

  • cgid

    Creator's group ID

  • mode

    Read/write permission

  • segsz

    Size of segment in bytes

  • lpid

    Process ID of last shared memory operation

  • cpid

    Process ID of creator

  • nattch

    Number of current attaches

  • atime

    Time of last attachment

  • dtime

    Time of last detachment

  • ctime

    Time of last of control structure

shared_chmod($var, $modebits)

Change the (lower 9) modebits of the shared memory object.

shared_chown($var, $uid, $gid = undef)

Change the owning uid and optionally gid of the shared memory object.

AUTHOR

Leon Timmermans, <leont at cpan.org>

BUGS

Please report any bugs or feature requests to bug-sysv-sharedmem at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=SysV-SharedMem. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

perldoc SysV::SharedMem

You can also look for information at:

ACKNOWLEDGEMENTS

LICENSE AND COPYRIGHT

Copyright 2010 Leon Timmermans.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.