<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation"> <title>gethostid()--Retrieve Host ID</title> <!-- Begin Header Records ========================================== --> <!-- All rights reserved. Licensed Materials Property of IBM --> <!-- US Government Users Restricted Rights --> <!-- Use, duplication or disclosure restricted by --> <!-- GSA ADP Schedule Contract with IBM Corp. --> <!-- Change History: --> <!-- Unix8 SCRIPT J converted by B2H R4.1 (346) (CMS) by V2KEA304 --> <!-- at RCHVMW2 on 17 Feb 1999 at 11:05:09 --> <!-- Edited by Kersten Feb 02 --> <link rel="stylesheet" type="text/css" href="../rzahg/ic.css"> </head> <body> <!--End Header Records --> <!-- Java sync-link --> <script type="text/javascript" language="Javascript" src="../rzahg/synch.js"> </script> <a name="Top_Of_Page"></a> <h2>gethostid()--Retrieve Host ID</h2> <div class="box" style="width: 80%;"> <br> Syntax<br> <pre> #include <sys/types.h> #include <sys/socket.h> int gethostid() </pre> <br> Service Program Name: QSOSRV1<br> <!-- iddvc RMBR --> <br> Default Public Authority: *USE<br> <!-- iddvc RMBR --> <br> nbsp;Threadsafe: Yes<br> <!-- iddvc RMBR --> <br> </div> <p>The <em>gethostid()</em> function is used to retrieve a host's ID.</p> <br> <h3>Authorities</h3> <p>No authorization is required.</p> <br> <h3>Return Value</h3> <p><em>gethostid()</em> returns an integer. Possible values are:</p> <ul> <li>0 when a <em>sethostid()</em> has not been issued previously since the last initial program load (IPL)<br> <br> </li> <li>n (successful), where n is the number specified on a previously issued <em>sethostid()</em> call</li> </ul> <br> <h3>Usage Notes</h3> <ol> <li>When a process issues a <em>sethostid()</em>, the <em>host_id</em> can be accessed by any process that issues a <em>gethostid()</em><br> <br> </li> <li>The <em>host_id</em> is reset to zero when an initial program load is performed.<br> <br> </li> <li>The <em>host_id</em> is a signed integer. Therefore, a -1 return value from the <em>gethostid()</em> may not indicate an error, but rather that a previous <em>sethostid()</em> was issued that specified a <em>host_id</em> of -1.<br> <br> </li> <li>While many socket implementations refer to the <em>host_id</em> as the IP address of the machine, this is not necessarily the case. Many machines that support the TCP/IP protocol suite support multiple local IP addresses. The value contained in <em>host_id</em> is <strong>not</strong> used by TCP in any manner.</li> </ol> <br> <h3>Related Information</h3> <ul> <li><a href="shosti.htm">sethostid()</a>--Set Host ID Address<br> <br> </li> <li><a href="ghostn.htm">gethostname()</a>--Retrieve Host Name<br> <br> </li> <li><a href="shostn.htm">sethostname()</a>--Set Host Name</li> </ul> <br> <hr> API introduced: V3R1 <hr> <center> <table cellpadding="2" cellspacing="2"> <tr align="center"> <td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> | <a href= "unix.htm">UNIX-Type APIs</a> | <a href="aplist.htm">APIs by category</a></td> </tr> </table></center> </body> </html>