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.IX Title "IPC::Semaphore 3perl"
.TH IPC::Semaphore 3perl 2023-11-30 "perl v5.38.2" "Perl Programmers Reference Guide"
.\" 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::Semaphore \- SysV Semaphore IPC object class
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\&    use IPC::SysV qw(IPC_PRIVATE S_IRUSR S_IWUSR IPC_CREAT);
\&    use IPC::Semaphore;
\&
\&    $sem = IPC::Semaphore\->new(IPC_PRIVATE, 10, S_IRUSR | S_IWUSR | IPC_CREAT);
\&
\&    $sem\->setall( (0) x 10);
\&
\&    @sem = $sem\->getall;
\&
\&    $ncnt = $sem\->getncnt;
\&
\&    $zcnt = $sem\->getzcnt;
\&
\&    $ds = $sem\->stat;
\&
\&    $sem\->remove;
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
A class providing an object based interface to SysV IPC semaphores.
.SH METHODS
.IX Header "METHODS"
.IP "new ( KEY , NSEMS , FLAGS )" 4
.IX Item "new ( KEY , NSEMS , FLAGS )"
Create a new semaphore set associated with \f(CW\*(C`KEY\*(C'\fR. \f(CW\*(C`NSEMS\*(C'\fR is the number
of semaphores in the set. A new set 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 semaphore identifier
associated with it, and \f(CW\*(C`\fR\f(CIFLAGS\fR\f(CW & IPC_CREAT\*(C'\fR is true.
.RE
.RS 4
.Sp
On creation of a new semaphore set \f(CW\*(C`FLAGS\*(C'\fR 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.
.RE
.IP getall 4
.IX Item "getall"
Returns the values of the semaphore set as an array.
.IP "getncnt ( SEM )" 4
.IX Item "getncnt ( SEM )"
Returns the number of processes waiting for the semaphore \f(CW\*(C`SEM\*(C'\fR to
become greater than its current value
.IP "getpid ( SEM )" 4
.IX Item "getpid ( SEM )"
Returns the process id of the last process that performed an operation
on the semaphore \f(CW\*(C`SEM\*(C'\fR.
.IP "getval ( SEM )" 4
.IX Item "getval ( SEM )"
Returns the current value of the semaphore \f(CW\*(C`SEM\*(C'\fR.
.IP "getzcnt ( SEM )" 4
.IX Item "getzcnt ( SEM )"
Returns the number of processes waiting for the semaphore \f(CW\*(C`SEM\*(C'\fR to
become zero.
.IP id 4
.IX Item "id"
Returns the system identifier for the semaphore set.
.IP "op ( OPLIST )" 4
.IX Item "op ( OPLIST )"
\&\f(CW\*(C`OPLIST\*(C'\fR is a list of operations to pass to \f(CW\*(C`semop\*(C'\fR. \f(CW\*(C`OPLIST\*(C'\fR is
a concatenation of smaller lists, each which has three values. The
first is the semaphore number, the second is the operation and the last
is a flags value. See \fBsemop\fR\|(2) for more details. For example
.Sp
.Vb 4
\&    $sem\->op(
\&        0, \-1, IPC_NOWAIT,
\&        1,  1, IPC_NOWAIT
\&    );
.Ve
.IP remove 4
.IX Item "remove"
Remove and destroy the semaphore set from the system.
.IP "set ( STAT )" 4
.IX Item "set ( STAT )"
.PD 0
.IP "set ( NAME => VALUE [, NAME => VALUE ...] )" 4
.IX Item "set ( NAME => VALUE [, NAME => VALUE ...] )"
.PD
\&\f(CW\*(C`set\*(C'\fR will set the following values of the \f(CW\*(C`stat\*(C'\fR structure associated
with the semaphore set.
.Sp
.Vb 3
\&    uid
\&    gid
\&    mode (only the permission bits)
.Ve
.Sp
\&\f(CW\*(C`set\*(C'\fR accepts either a stat object, as returned by the \f(CW\*(C`stat\*(C'\fR method,
or a list of \fIname\fR\-\fIvalue\fR pairs.
.IP "setall ( VALUES )" 4
.IX Item "setall ( VALUES )"
Sets all values in the semaphore set to those given on the \f(CW\*(C`VALUES\*(C'\fR list.
\&\f(CW\*(C`VALUES\*(C'\fR must contain the correct number of values.
.IP "setval ( N , VALUE )" 4
.IX Item "setval ( N , VALUE )"
Set the \f(CW\*(C`N\*(C'\fRth value in the semaphore set to \f(CW\*(C`VALUE\*(C'\fR
.IP stat 4
.IX Item "stat"
Returns an object of type \f(CW\*(C`IPC::Semaphore::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 your system documentation.
.Sp
.Vb 8
\&    uid
\&    gid
\&    cuid
\&    cgid
\&    mode
\&    ctime
\&    otime
\&    nsems
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
IPC::SysV, Class::Struct, \fBsemget\fR\|(2), \fBsemctl\fR\|(2), \fBsemop\fR\|(2)
.SH AUTHORS
.IX Header "AUTHORS"
Graham Barr <gbarr@pobox.com>,
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.