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+.\" Copyright (c) 1996 John Birrell <jb@cimlogic.com.au>.
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"	This product includes software developed by John Birrell.
+.\" 4. Neither the name of the author nor the names of any co-contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.Dd April 4, 1996
+.Dt PTHREAD_ONCE 3
+.Os BSD 4
+.Sh NAME
+.Nm pthread_once
+.Nd dynamic package initialization
+.Sh SYNOPSIS
+.Fd #include <pthread.h>
+.Pp
+pthread_once
+.Fa once_control
+= PTHREAD_ONCE_INIT;
+.Ft int
+.Fn pthread_once "pthread_once_t *once_control" "void (*init_routine)(void)"
+.Sh DESCRIPTION
+The first call to
+.Fn pthread_once
+by any thread in a process, with a given
+.Fa once_control ,
+will call the
+.Fn init_routine
+with no arguments. Subsequent calls to
+.Fn pthread_once
+with the same
+.Fa once_control
+will not call the
+.Fn init_routine .
+On return from
+.Fn pthread_once ,
+it is guaranteed that
+.Fn init_routine
+has completed. The
+.Fa once_control
+parameter is used to determine whether the associated initialization
+routine has been called.
+.Pp
+The function
+.Fn pthread_once
+is not a cancellation point. However, if
+.Fn init_routine
+is a cancellation point and is cancelled, the effect on
+.Fa once_control is as if 
+.Fn pthread_once
+was never called.
+.Pp
+The constant
+.Fa PTHREAD_ONCE_INIT
+is defined by header
+.Aq Pa pthread.h .
+.Pp
+The behavior of
+.Fn pthread_once
+is undefined if
+.Fa once_control
+has automatic storage duration or is not initialized by
+.Fa PTHREAD_ONCE_INIT .
+.Pp
+.Sh RETURN VALUES
+If successful,  the
+.Fn pthread_once
+function will return zero. Otherwise an error number will be returned to
+indicate the error.
+.Sh ERRORS
+None.
+.Pp
+.Sh SEE ALSO
+.Xr pthreads 3
+.Sh STANDARDS
+.Fn pthread_once
+conforms to ISO/IEC 9945-1 ANSI/IEEE
+.Pq Dq Tn POSIX
+Std 1003.1 Second Edition 1996-07-12.