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.\" ========================================================================
.\"
.IX Title "IPC::SharedMem 3"
.TH IPC::SharedMem 3 "2021-08-09" "perl v5.32.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
IPC::SharedMem \- SysV Shared Memory IPC object class
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&    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;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
A class providing an object based interface to SysV \s-1IPC\s0 shared memory.
.SH "METHODS"
.IX Header "METHODS"
.IP "new ( \s-1KEY , SIZE , FLAGS\s0 )" 4
.IX Item "new ( KEY , SIZE , FLAGS )"
Creates a new shared memory segment of \f(CW\*(C`SIZE\*(C'\fR bytes size associated
with \f(CW\*(C`KEY\*(C'\fR. A new segment is created if
.RS 4
.IP "\(bu" 4
\&\f(CW\*(C`KEY\*(C'\fR is equal to \f(CW\*(C`IPC_PRIVATE\*(C'\fR
.IP "\(bu" 4
\&\f(CW\*(C`KEY\*(C'\fR does not already have a shared memory segment associated
with it, and \f(CW\*(C`\f(CIFLAGS\f(CW & IPC_CREAT\*(C'\fR is true.
.RE
.RS 4
.Sp
On creation of a new shared memory segment \f(CW\*(C`FLAGS\*(C'\fR is used to
set the permissions.  Be careful not to set any flags that the
Sys V \s-1IPC\s0 implementation does not allow: in some systems setting
execute bits makes the operations fail.
.RE
.IP "id" 4
.IX Item "id"
Returns the shared memory identifier.
.IP "read ( \s-1POS, SIZE\s0 )" 4
.IX Item "read ( POS, SIZE )"
Read \f(CW\*(C`SIZE\*(C'\fR bytes from the shared memory segment at \f(CW\*(C`POS\*(C'\fR. Returns
the string read, or \f(CW\*(C`undef\*(C'\fR if there was an error. The return value
becomes tainted. See shmread.
.IP "write ( \s-1STRING, POS, SIZE\s0 )" 4
.IX Item "write ( STRING, POS, SIZE )"
Write \f(CW\*(C`SIZE\*(C'\fR bytes to the shared memory segment at \f(CW\*(C`POS\*(C'\fR. Returns
true if successful, or false if there is an error. See shmwrite.
.IP "remove" 4
.IX Item "remove"
Remove the shared memory segment from the system or mark it as
removed as long as any processes are still attached to it.
.IP "is_removed" 4
.IX Item "is_removed"
Returns true if the shared memory segment has been removed or
marked for removal.
.IP "stat" 4
.IX Item "stat"
Returns an object of type \f(CW\*(C`IPC::SharedMem::stat\*(C'\fR which is a sub-class
of \f(CW\*(C`Class::Struct\*(C'\fR. It provides the following fields. For a description
of these fields see you system documentation.
.Sp
.Vb 12
\&    uid
\&    gid
\&    cuid
\&    cgid
\&    mode
\&    segsz
\&    lpid
\&    cpid
\&    nattch
\&    atime
\&    dtime
\&    ctime
.Ve
.IP "attach ( [\s-1FLAG\s0] )" 4
.IX Item "attach ( [FLAG] )"
Permanently attach to the shared memory segment. When a \f(CW\*(C`IPC::SharedMem\*(C'\fR
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 \fBshmat\fR\|(2).
.IP "detach" 4
.IX Item "detach"
Detach from the shared memory segment that previously has been attached
to. Returns true if successful, or false on error. See \fBshmdt\fR\|(2).
.IP "addr" 4
.IX Item "addr"
Returns the address of the shared memory that has been attached to in a
format suitable for use with \f(CW\*(C`pack(\*(AqP\*(Aq)\*(C'\fR. Returns \f(CW\*(C`undef\*(C'\fR if the shared
memory has not been attached.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
IPC::SysV, Class::Struct
.SH "AUTHORS"
.IX Header "AUTHORS"
Marcus Holland-Moritz <mhx@cpan.org>
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Version 2.x, Copyright (C) 2007\-2013, Marcus Holland-Moritz.
.PP
Version 1.x, Copyright (c) 1997, Graham Barr.
.PP
This program is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
