NetBSD/lib/libpthread/pthread_cond_init.3

.\" $NetBSD: pthread_cond_init.3,v 1.7 2005/06/17 18:26:53 wiz Exp $
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.\" Copyright (c) 1997 Brian Cully <shmit@kublai.com>
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.\" $FreeBSD: src/lib/libpthread/man/pthread_cond_init.3,v 1.13 2002/09/16 19:29:28 mini Exp $
.\"
.Dd January 30, 2003
.Dt PTHREAD_COND_INIT 3
.Os
.Sh NAME
.Nm pthread_cond_init
.Nd create a condition variable
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_cond_init "pthread_cond_t * restrict cond" "const pthread_condattr_t * restrict attr"
.Sh DESCRIPTION
The
.Fn pthread_cond_init
function creates a new condition variable, with attributes specified with
.Fa attr .
If
.Fa attr
is NULL the default attributes are used.
.Pp
Condition variables are intended to be used to communicate changes in
the state of data shared between threads.
Condition variables are always associated with a mutex to provide
synchronized access to the shared data.
A single predicate should always be associated with a
condition variable.
The predicate should identify a state of the
shared data that must be true before the thread proceeds.
.Sh RETURN VALUES
If successful, the
.Fn pthread_cond_init
function will return zero and put the new condition variable id into
.Fa cond ,
otherwise an error number will be returned to indicate the error.
.Sh ERRORS
.Fn pthread_cond_init
shall fail if:
.Bl -tag -width Er
.It Bq Er ENOMEM
The process cannot allocate enough memory to initialize another condition
variable.
.It Bq Er EAGAIN
The system lacks the resources to initialize another condition variable.
.El
.Pp
.Fn pthread_cond_init
may fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value specified by
.Fa attr
is invalid.
.El
.Sh SEE ALSO
.Xr pthread_cond_broadcast 3 ,
.Xr pthread_cond_destroy 3 ,
.Xr pthread_cond_signal 3 ,
.Xr pthread_cond_timedwait 3 ,
.Xr pthread_cond_wait 3
.Sh STANDARDS
.Fn pthread_cond_init
conforms to
.St -p1003.1-96 .