1IPC::SharedMem(3)     User Contributed Perl Documentation    IPC::SharedMem(3)
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NAME

6       IPC::SharedMem - SysV Shared Memory IPC object class
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SYNOPSIS

9           use IPC::SysV qw(IPC_PRIVATE S_IRUSR S_IWUSR);
10           use IPC::SharedMem;
11
12           $shm = IPC::SharedMem->new(IPC_PRIVATE, 8, S_IRWXU);
13
14           $shm->write(pack("S", 4711), 2, 2);
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16           $data = $shm->read(0, 2);
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18           $ds = $shm->stat;
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20           $shm->remove;
21

DESCRIPTION

23       A class providing an object based interface to SysV IPC shared memory.
24

METHODS

26       new ( KEY , SIZE , FLAGS )
27           Creates a new shared memory segment of "SIZE" bytes size associated
28           with "KEY". A new segment is created if
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30           •   "KEY" is equal to "IPC_PRIVATE"
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32           •   "KEY" does not already have a shared memory segment associated
33               with it, and "FLAGS & IPC_CREAT" is true.
34
35           On creation of a new shared memory segment "FLAGS" is used to set
36           the permissions.  Be careful not to set any flags that the Sys V
37           IPC implementation does not allow: in some systems setting execute
38           bits makes the operations fail.
39
40       id  Returns the shared memory identifier.
41
42       read ( POS, SIZE )
43           Read "SIZE" bytes from the shared memory segment at "POS". Returns
44           the string read, or "undef" if there was an error. The return value
45           becomes tainted. See shmread.
46
47       write ( STRING, POS, SIZE )
48           Write "SIZE" bytes to the shared memory segment at "POS". Returns
49           true if successful, or false if there is an error. See shmwrite.
50
51       remove
52           Remove the shared memory segment from the system or mark it as
53           removed as long as any processes are still attached to it.
54
55       is_removed
56           Returns true if the shared memory segment has been removed or
57           marked for removal.
58
59       stat
60           Returns an object of type "IPC::SharedMem::stat" which is a sub-
61           class of "Class::Struct". It provides the following fields. For a
62           description of these fields see you system documentation.
63
64               uid
65               gid
66               cuid
67               cgid
68               mode
69               segsz
70               lpid
71               cpid
72               nattch
73               atime
74               dtime
75               ctime
76
77       attach ( [FLAG] )
78           Permanently attach to the shared memory segment. When a
79           "IPC::SharedMem" object is attached, it will use memread and
80           memwrite instead of shmread and shmwrite for accessing the shared
81           memory segment.  Returns true if successful, or false on error. See
82           shmat(2).
83
84       detach
85           Detach from the shared memory segment that previously has been
86           attached to. Returns true if successful, or false on error. See
87           shmdt(2).
88
89       addr
90           Returns the address of the shared memory that has been attached to
91           in a format suitable for use with "pack('P')". Returns "undef" if
92           the shared memory has not been attached.
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SEE ALSO

95       IPC::SysV, Class::Struct
96

AUTHORS

98       Marcus Holland-Moritz <mhx@cpan.org>
99

101       Version 2.x, Copyright (C) 2007-2013, Marcus Holland-Moritz.
102
103       Version 1.x, Copyright (c) 1997, Graham Barr.
104
105       This program is free software; you can redistribute it and/or modify it
106       under the same terms as Perl itself.
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110perl v5.36.0                      2022-07-22                 IPC::SharedMem(3)
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