NAME

SysV::SharedMem - SysV Shared memory made easy

VERSION

version 0.008

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.

FUNCTIONS

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 segment is created (if $mode is '>' or '+>'). Default is 0600.

• 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@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2010 by Leon Timmermans.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.