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3.4 KiB
HTML
83 lines
3.4 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML>
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<HEAD>
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<META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=utf-8">
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<TITLE>PTHREAD_ONCE(3) manual page</TITLE>
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<META NAME="GENERATOR" CONTENT="OpenOffice.org 1.1.3 (Linux)">
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<META NAME="CREATED" CONTENT="20050505;322600">
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<META NAME="CHANGED" CONTENT="20050603;463100">
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</HEAD>
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<BODY LANG="en-GB" BGCOLOR="#ffffff" DIR="LTR">
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<H4>POSIX Threads for Windows – REFERENCE - <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A></H4>
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<P><A HREF="index.html">Reference Index</A></P>
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<P><A HREF="#toc">Table of Contents</A></P>
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<H2><A HREF="#toc0" NAME="sect0">Name</A></H2>
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<P>pthread_once - once-only initialization
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</P>
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<H2><A HREF="#toc1" NAME="sect1">Synopsis</A></H2>
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<P><B>#include <pthread.h></B>
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</P>
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<P><B>pthread_once_t </B><I>once_control</I> <B>= PTHREAD_ONCE_INIT;</B>
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</P>
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<P><B>int pthread_once(pthread_once_t *</B><I>once_control</I><B>,
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void (*</B><I>init_routine</I><B>) (void));</B>
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</P>
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<H2><A HREF="#toc2" NAME="sect2">Description</A></H2>
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<P>The purpose of <B>pthread_once</B> is to ensure that a piece of
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initialization code is executed at most once. The <I>once_control</I>
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argument points to a static or extern variable statically initialized
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to <B>PTHREAD_ONCE_INIT</B>.
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</P>
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<P>The first time <B>pthread_once</B> is called with a given
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<I>once_control</I> argument, it calls <I>init_routine</I> with no
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argument and changes the value of the <I>once_control</I> variable to
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record that initialization has been performed. Subsequent calls to
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<B>pthread_once</B> with the same <B>once_control</B> argument do
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nothing.
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</P>
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<H2><A HREF="#toc3" NAME="sect3">Cancellation</A></H2>
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<P>While <B>pthread_once</B> is not a cancellation point,
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<I>init_routine</I> can be. The effect on <I>once_control</I> of a
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cancellation inside the <I>init_routine</I> is to leave it as if
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<B>pthread_once</B> had not been called by the cancelled thread.</P>
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<H2><A HREF="#toc4" NAME="sect4">Return Value</A></H2>
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<P STYLE="text-decoration: none"><FONT COLOR="#000000"><B>pthread_once</B>
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returns 0 on success, or an error code on failure.</FONT></P>
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<H2><A HREF="#toc5" NAME="sect5">Errors</A></H2>
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<P>The <B>pthread_once</B> function returns the following error code
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on error:
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</P>
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<DL>
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<DL>
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<DT STYLE="margin-right: 1cm; margin-bottom: 0.5cm"><B>EINVAL</B>
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</DT></DL>
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</DL>
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<P STYLE="margin-left: 2cm">
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The once_control or init_routine parameter is NULL.</P>
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<H2><A HREF="#toc6" NAME="sect6">Author</A></H2>
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<P>Xavier Leroy <Xavier.Leroy@inria.fr>
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</P>
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<P>Modified by Ross Johnson for use with <A HREF="http://sources.redhat.com/pthreads-win32">Pthreads-w32</A>.</P>
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<HR>
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<P><A NAME="toc"></A><B>Table of Contents</B></P>
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<UL>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect0" NAME="toc0">Name</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect1" NAME="toc1">Synopsis</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect2" NAME="toc2">Description</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect3" NAME="toc3">Cancellation</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect4" NAME="toc4">Return
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Value</A>
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</P>
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<LI><P STYLE="margin-bottom: 0cm"><A HREF="#sect5" NAME="toc5">Errors</A>
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</P>
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<LI><P><A HREF="#sect6" NAME="toc6">Author</A>
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</P>
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</UL>
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</BODY>
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</HTML>
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