230 lines
7.4 KiB
HTML
230 lines
7.4 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>getgroups()--Get Group IDs</title>
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<!-- Begin Header Records ========================================= -->
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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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<!-- Change History: -->
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<!-- file cleaned -->
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<!-- Unix2 SCRIPT J converted by B2H R4.1 (346) (CMS) by V2KEA304 -->
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<!-- at RCHVMW2 on 17 Feb 1999 at 11:05:09 -->
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<!-- File cleanup completed Feb 2002 by v2cdijab -->
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<!-- This file has undergone html cleanup on 05/14/02 by JET -->
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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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<!-- End Header Records -->
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<!-- Java sync-link -->
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<script type="text/javascript" language="Javascript" src="../rzahg/synch.js">
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</script>
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<a name="Top_Of_Page"></a>
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<h2>getgroups()--Get Group IDs</h2>
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<!-- =========================================== -->
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<!-- S Y N T A X / P A R M T A B L E -->
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<!-- =========================================== -->
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<div class="box" style="width: 70%;">
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<br>
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Syntax<br>
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<pre>
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#include <unistd.h>
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int getgroups(int <em>gidsetsize</em>, gid_t <em>grouplist</em>[])
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</pre>
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Service Program Name: QSYPAPI<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: No<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<!-- =========================================== -->
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<!-- D E F I N I T I O N -->
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<!-- =========================================== -->
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<p>If the <em>gidsetsize</em> argument is zero, <strong>getgroups()</strong>
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returns the number of group IDs associated with the calling thread without
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modifying the array pointed to by the <em>grouplist</em> argument. The number
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of group IDs includes the effective group ID and the supplementary group IDs.
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Otherwise, <strong>getgroups()</strong> fills in the array <em>grouplist</em>
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with the effective group ID and supplementary group IDs of the calling thread
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and returns the actual number of group IDs stored. The values of array entries
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with indexes larger than or equal to the returned value are undefined.</p>
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<br>
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<!-- =========================================== -->
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<!-- P A R A M E T E R S -->
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<!-- =========================================== -->
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<h3>Parameters</h3>
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<!-- Parameter 1 -->
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<dl>
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<dt><strong><em>gidsetsize</em></strong></dt>
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<dd>(Input) The number of elements in the supplied array <em>
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grouplist</em>.<br>
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<br>
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</dd>
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<!-- Parameter 2 -->
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<dt><strong><em>grouplist</em></strong></dt>
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<dd>(Output) The effective group ID and supplementary group IDs. The first
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element in <em>grouplist</em> is the effective group ID.</dd>
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</dl>
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<br>
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<!-- =========================================== -->
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<!-- A U T H O R I T I E S A N D L O C K S -->
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<!-- =========================================== -->
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<h3>Authorities</h3>
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<p>No authorization is required.</p>
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<br>
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<!-- =========================================== -->
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<!-- R E T U R N V A L U E -->
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<!-- =========================================== -->
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<h3>Return Value</h3>
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<table cellpadding="5">
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<!-- cols="15 85" -->
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<tr>
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<td align="left" valign="top" nowrap><em>0 or > 0</em></td>
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<td align="left" valign="top"><strong>getgroups()</strong> was successful. If
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the <em>gidsetsize</em> argument is 0, the number of group IDs is returned.
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This number includes the effective group ID and supplementary group IDs. If
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<em>gidsetsize</em> is greater than 0, the array <em>grouplist</em> is filled
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with the effective group ID and supplementary group IDs of the calling thread
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and the return value represents the actual number of group IDs stored.</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>-1</em></td>
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<td align="left" valign="top"><strong>getgroups()</strong> was not successful.
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The <em>errno</em> global variable is set to indicate the error.</td>
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</tr>
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</table>
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<br>
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<br>
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<!-- =========================================== -->
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<!-- E R R O R C O N D I T I O N S -->
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<!-- =========================================== -->
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<h3>Error Conditions</h3>
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<p>If <strong>getgroups()</strong> is not successful, <em>errno</em> usually
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indicates one of the following errors. Under some conditions, <em>errno</em>
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could indicate an error other than those listed here.</p>
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<table cellpadding="5">
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<!-- cols="25 75" -->
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<tr>
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<th align="left" valign="bottom">Error condition</th>
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<th align="left" valign="bottom">Additional information</th>
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</tr>
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<tr>
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<td align="left" valign="top">
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<em>[<a href="unix14.htm#EINVAL">EINVAL</a>]</em></td>
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<td align="left" valign="top">
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<p>The <em>gidsetsize</em> argument is not equal to zero and is less than the
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number of group IDs.</p>
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</td>
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</tr>
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</table>
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<br>
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<!-- =========================================== -->
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<!-- U S A G E N O T E S -->
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<!-- =========================================== -->
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<h3><a name="USAGE_NOTES">Usage Notes</a></h3>
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<p>This function can be used in two different ways. First, if called with <em>
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gidsetsize</em> equal to 0, it is used to return the number of groups
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associated with a thread. Second, if called with <em>gidsetsize</em> not equal
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to 0, it is used to return a list of the <samp>GID</samp>s representing the
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effective and supplementary groups associated with a thread. In this case, the
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<em>gidsetsize</em> argument represents how much space is available in the <em>
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grouplist</em> argument.</p>
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<p>The calling routine can choose to call this function with <em>
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gidsetsize</em> equal to 0 to determine how much space to allocate for a second
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call to this function. The second call returns the values. The following is an
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example of this method:</p>
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<pre>
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int numgroups;
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gid_t *grouplist;
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numgroups = getgroups(0,NULL);
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grouplist = (gid_t *) calloc( numgroups, sizeof(gid_t) );
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if (getgroups( numgroups, grouplist) != -1) {
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.
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.
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}
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</pre>
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<p>Alternatively, the calling routine can choose to create enough space for
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NGROUPS_MAX entries to ensure enough space is available for the maximum
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possible number of entries that may be returned. This introduces the
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possibility of wasted space. The following is an example of this method:</p>
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<pre>
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int numgroups;
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gid_t grouplist[ NGROUPS_MAX ];
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if ( getgroups( NGROUPS_MAX, grouplist ) != -1 ) {
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.
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.
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}
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</pre>
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<br>
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<!-- =========================================== -->
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<!-- R E L A T E D I N F O R M A T I O N -->
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<!-- =========================================== -->
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<h3>Related Information</h3>
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<ul>
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<li>The <<strong>unistd.h</strong>> file (see <a href="unix13.htm">Header
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Files for UNIX-Type Functions</a>)</li>
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</ul>
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<br>
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<hr>
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API introduced: V3R1
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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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"unix.htm">UNIX-Type APIs</a> | <a href="aplist.htm">APIs by 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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