188 lines
4.7 KiB
HTML
188 lines
4.7 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 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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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>pthread_is_multithreaded_np()--Check Current Number of Threads</title>
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Begin Header Records ========================================== -->
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<!-- NETMG2 SCRIPT A converted by B2H R4.1 (346) (CMS) by HOLTJM at -->
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<!-- RCHVMW2 on 29 Jan 1999 at 10:01:37 -->
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<!--File Edited November 2001 -->
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<!--End Header Records -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<!-- Java sync-link -->
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<script language="Javascript" src="../rzahg/synch.js" type="text/javascript">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>pthread_is_multithreaded_np()--Check Current Number of Threads</h2>
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<div class="box" style="width: 50%;">
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<br>
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Syntax:
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<pre>
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#include <pthread.h>
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unsigned int pthread_is_multithreaded_np(void);
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</pre>
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Service Program Name: QP0WPTHR<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE<br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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Signal Safe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <strong>pthread_is_multithreaded_np</strong>() function returns true or
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false, indicating whether the current process has more than one thread. A
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return value of zero indicates that the calling thread is the only thread in
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the process. A value not equal to zero, indicates that there were multiple
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other threads in the process at the time of the call to
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<strong>pthread_is_multithreaded_np</strong>().</p>
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<p>The total number of threads currently in the process can be determined by
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adding 1 to the return value of
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<strong>pthread_is_multithreaded_np</strong>().</p>
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<p><strong>Note:</strong> This function is not portable.</p>
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<br>
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<h3>Authorities and Locks</h3>
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<p>None.</p>
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<br>
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<h3>Parameters</h3>
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<p>None.</p>
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<br>
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<h3>Return Value</h3>
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<dl>
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<dt><strong>0</strong></dt>
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<dd>No other threads exist in the process.<br><br></dd>
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<dt><strong>value</strong></dt>
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<dd>There are currently <em>value+1</em> total threads in the process.</dd>
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</dl>
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<br>
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<h3>Error Conditions</h3>
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<p>None.</p>
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<br>
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<h3>Related Information</h3>
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<ul>
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<li>The <<strong>pthread.h</strong>> header file. See <a href=
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"rzah4hed.htm">Header files for Pthread functions</a>.<br><br></li>
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<li><a href="users_99.htm">pthread_is_initialthread_np()</a>--Check if Running in
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the Initial Thread</li>
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</ul>
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<br>
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<h3>Example</h3>
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<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
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for information pertaining to code examples.</p>
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<pre>
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#define _MULTI_THREADED
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#include <pthread.h>
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#include <stdio.h>
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#include "check.h"
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#define NUMTHREADS 3
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void *threadfunc(void *parm)
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{
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int myHiId;
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int myId;
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pthread_t me = pthread_self();
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printf("Inside the New Thread\n");
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sleep(2); /* Sleep is not a very robust way to serialize threads */
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return NULL;
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}
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int main(int argc, char **argv)
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{
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pthread_t thread[NUMTHREADS];
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int rc=0;
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int theHiId=0;
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int theId=0;
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int i=0;
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printf("Enter Testcase - %s\n", argv[0]);
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printf("Create %d threads\n", NUMTHREADS);
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for (i=0; i<NUMTHREADS; ++i) {
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rc = pthread_create(&thread[i], NULL, threadfunc, NULL);
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checkResults("pthread_create()\n", rc);
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printf("Main: Currently %d threads\n",
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pthread_is_multithreaded_np() + 1);
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}
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printf("Join to threads\n");
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for (i=0; i<NUMTHREADS; ++i) {
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rc = pthread_join(thread[i], NULL);
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checkResults("pthread_join()\n", rc);
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}
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if (rc = pthread_is_multithreaded_np()) {
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printf("Error: %d Threads still exist!\n", rc+1);
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exit(1);
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}
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printf("Main completed\n");
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return 0;
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}
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</pre>
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<p><strong>Output:</strong></p>
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<pre>
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Enter Testcase - QP0WTEST/TPISMT0
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Create 3 threads
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Main: Currently 2 threads
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Main: Currently 3 threads
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Main: Currently 4 threads
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Join to threads
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Inside the New Thread
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Inside the New Thread
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Inside the New Thread
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Main completed
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</pre>
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<br>
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<hr>API introduced: V4R3
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<hr>
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<center>
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<table cellpadding="2" cellspacing="2">
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<tr align="center">
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<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href=
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"rzah4mst.htm">Pthread APIs</a> | <a href="aplist.htm">APIs by
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category</a></td>
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</tr>
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</table>
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</center>
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</body>
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</html>
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