357 lines
11 KiB
HTML
357 lines
11 KiB
HTML
|
<!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>gethostbyname()--Get Host Information for Host Name</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>gethostbyname()--Get Host Information for Host Name</h2>
|
||
|
|
|
||
|
|
<div class="box" style="width: 70%;">
|
||
|
|
<br> BSD 4.3 Syntax<br>
|
||
|
|
<pre>
|
||
|
|
#include <netdb.h>
|
||
|
|
|
||
|
|
struct hostent *gethostbyname(char *<em>host_name</em>)
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
Service Program Name: QSOSRV2<br>
|
||
|
|
<!-- iddvc RMBR -->
|
||
|
|
<br>
|
||
|
|
Default Public Authority: *USE<br>
|
||
|
|
<!-- iddvc RMBR -->
|
||
|
|
<br>
|
||
|
|
Threadsafe: No; see <a href="#USAGE_NOTES">Usage Notes</a>.<br>
|
||
|
|
<!-- iddvc RMBR -->
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
|
||
|
|
<div class="box" style="width: 70%;">
|
||
|
|
<br>
|
||
|
|
<a href="_xopen_source.htm">UNIX 98 Compatible Syntax</a><br>
|
||
|
|
<pre>
|
||
|
|
#define _XOPEN_SOURCE 520
|
||
|
|
#include <netdb.h>
|
||
|
|
|
||
|
|
struct hostent *gethostbyname(const char *<em>host_name</em>)
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
Service Program Name: QSOSRV2<br>
|
||
|
|
<!-- iddvc RMBR -->
|
||
|
|
<br>
|
||
|
|
Default Public Authority: *USE<br>
|
||
|
|
<!-- iddvc RMBR -->
|
||
|
|
<br>
|
||
|
|
Threadsafe: No; see <a href="#USAGE_NOTES">Usage Notes</a>.<br>
|
||
|
|
<!-- iddvc RMBR -->
|
||
|
|
<br>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<p>The <em>gethostbyname()</em> function is used to retrieve information about
|
||
|
|
a host.</p>
|
||
|
|
|
||
|
|
<p>There are two versions of the API, as shown above. The base i5/OS API uses BSD 4.3
|
||
|
|
structures and syntax. The other uses syntax and structures compatible with the UNIX 98
|
||
|
|
programming interface specifications. You can select the UNIX 98 compatible
|
||
|
|
interface with the <a href="_xopen_source.htm">_XOPEN_SOURCE</a> macro.</p>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
|
||
|
|
|
||
|
|
<h3>Parameters</h3>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt><strong>host_name</strong></dt>
|
||
|
|
|
||
|
|
<dd>(Input) The pointer to the character string that contains the name of the
|
||
|
|
host for which information is to be retrieved.</dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Authorities</h3>
|
||
|
|
|
||
|
|
<p>Authorization of *R (allow access to the object) to the host aliases file
|
||
|
|
specified by the <em>HOSTALIASES</em> environment variable.</p>
|
||
|
|
|
||
|
|
<p>You also need *X authority to each directory in the path of the host aliases
|
||
|
|
file.</p>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
|
||
|
|
|
||
|
|
<h3>Return Value</h3>
|
||
|
|
|
||
|
|
<p><em>gethostbyname()</em> returns a pointer. Possible values are:</p>
|
||
|
|
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li>NULL (unsuccessful)<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>p (successful), where p is a pointer to <strong>struct
|
||
|
|
hostent</strong>.</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
|
||
|
|
<p>The structure <strong>struct hostent</strong> is defined in
|
||
|
|
<strong><netdb.h></strong>.</p>
|
||
|
|
|
||
|
|
<pre>
|
||
|
|
struct hostent {
|
||
|
|
char *h_name;
|
||
|
|
char **h_aliases;
|
||
|
|
int h_addrtype;
|
||
|
|
int h_length;
|
||
|
|
char **h_addr_list;
|
||
|
|
};
|
||
|
|
|
||
|
|
#define h_addr h_addr_list[0]
|
||
|
|
</pre>
|
||
|
|
|
||
|
|
<p><em>h_name</em> points to the character string that contains the name of the
|
||
|
|
host. <em>h_aliases</em> is a pointer to a NULL-terminated list of pointers,
|
||
|
|
each of which points to a character string that represents an alternative name
|
||
|
|
for the host. <em>h_addrtype</em> contains the address type of the host (for
|
||
|
|
example, <samp>AF_INET</samp>). <em>h_length</em> contains the address length.
|
||
|
|
<em>h_addr_list</em> is a pointer to a NULL-terminated list of pointers, each
|
||
|
|
of which points to a network address for the host, in network byte order. Note
|
||
|
|
that the array of address pointers points to structures of type
|
||
|
|
<strong>in_addr</strong> defined in <strong><netinet/in.h></strong>.</p>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<h3>Error Conditions</h3>
|
||
|
|
|
||
|
|
<p>When <em>gethostbyname()</em> fails, <em>h_errno</em> (defined in
|
||
|
|
<strong><netdb.h></strong>) can be set to one of the following:</p>
|
||
|
|
<dl>
|
||
|
|
<dd></dd>
|
||
|
|
|
||
|
|
<dt><em>[HOST_NOT_FOUND]</em></dt>
|
||
|
|
<dd><p>The host name specified by the <em>host_name</em>
|
||
|
|
parameter was not found.</p></dd>
|
||
|
|
|
||
|
|
<dt><em>[NO_DATA]</em></dt>
|
||
|
|
<dd><p>The host name is a valid name, but there is no
|
||
|
|
corresponding IP address.</p></dd>
|
||
|
|
|
||
|
|
|
||
|
|
<dt><em>[NO_RECOVERY]</em></dt>
|
||
|
|
<dd><p>An unrecoverable error has occurred.</p></dd>
|
||
|
|
|
||
|
|
|
||
|
|
<dt><em>[TRY_AGAIN]</em></dt>
|
||
|
|
<dd><p>The local server did not receive a response from
|
||
|
|
an authoritative server. An attempt at a later time may succeed.</p></dd>
|
||
|
|
</dl>
|
||
|
|
<p>When the <em>gethostbyname()</em> function fails, <em>errno</em> can be set
|
||
|
|
to:</p>
|
||
|
|
<dl>
|
||
|
|
<dt><em>[EACCES]</em></dt>
|
||
|
|
<dd><p>Permission denied. The process does not have the
|
||
|
|
appropriate privileges to the host aliases file specified by the
|
||
|
|
<em>HOSTALIASES</em> environment variable.</p></dd>
|
||
|
|
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
|
||
|
|
|
||
|
|
<h3><a name="USAGE_NOTES">Usage Notes</a></h3>
|
||
|
|
|
||
|
|
<ol>
|
||
|
|
<li>The iSeries Navigator or the following CL commands can be
|
||
|
|
used to access the host database file:<br>
|
||
|
|
<br>
|
||
|
|
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li>ADDTCPHTE (Add TCP/IP Host Table Entry)<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>RMVTCPHTE (Remove TCP/IP Host Table Entry)<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>CHGTCPHTE (Change TCP/IP Host Table Entry)<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>RNMTCPHTE (Rename TCP/IP Host Table Entry)<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>MRGTCPHT (Merge TCP/IP Host Tables)</li>
|
||
|
|
</ul>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>The pointer returned by <em>gethostbyname()</em> points to static storage
|
||
|
|
that is overwritten on subsequent calls to the <em>gethostbyname()</em>,
|
||
|
|
<em>gethostbyaddr()</em>, or <em>gethostent()</em> functions.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>There are two sources from which host information can be obtained: the
|
||
|
|
domain name server, and the host database file. The path taken depends on
|
||
|
|
whether an IP address is configured for a name server using the iSeries Navigator or option 12,
|
||
|
|
Change TCP/IP domain information, on the Configure TCP/IP (CFGTCP) menu.
|
||
|
|
|
||
|
|
<p><strong>Note:</strong> A person with a UNIX background would expect this
|
||
|
|
information to exist in a file known as <strong>/etc/resolv.conf</strong>.</p>
|
||
|
|
|
||
|
|
<p>If the IP address is found (indicating that the local network is a domain
|
||
|
|
network), the <em>gethostbyaddr()</em> function attempts to query the domain
|
||
|
|
name server for information about a host. If the query fails, the information
|
||
|
|
is obtained from the host database file. If the name server IP address is not
|
||
|
|
found (indicating that local network is a flat network), the host database file
|
||
|
|
is used to obtain the address.</p>
|
||
|
|
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>If the <em>host_name</em> parameter does specify a domain qualified name,
|
||
|
|
the <em>gethostbyaddr()</em> function appends a domain name to the specified
|
||
|
|
host name, if possible. The domain name that is appended is configured using the
|
||
|
|
iSeries Navigator or CFGTCP menu option 12, Change TCP/IP domain information.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>When the host information is obtained from the host database file, the file
|
||
|
|
is opened and the host information is retrieved (if it exists) from the file.
|
||
|
|
The file is then closed only if a <em>sethostent()</em> with a nonzero
|
||
|
|
parameter value was not previously done.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>If a <em>sethostent()</em> with a nonzero parameter value was previously
|
||
|
|
done, the <em>gethostbyname()</em> routine, when obtaining host information
|
||
|
|
from the domain name server, communicates with the domain name server over a
|
||
|
|
connection-oriented transport service (for example, TCP). Otherwise,
|
||
|
|
<em>gethostbyname()</em> uses a connectionless transport service (for example,
|
||
|
|
UDP).<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>A job has a coded character set identifier (CCSID) and a default CCSID. The
|
||
|
|
default CCSID is the same as the job CCSID unless the job CCSID specifies
|
||
|
|
65535, which requests that no database translation be performed. In this case,
|
||
|
|
the default CCSID is set by the system based on the language ID in effect for
|
||
|
|
the job.
|
||
|
|
|
||
|
|
<p>If the host information is retrieved from the domain name server, sockets
|
||
|
|
converts the host name specified by the <em>host_name</em> parameter from the
|
||
|
|
default (CCSID) to ASCII before communicating with the domain name server. If
|
||
|
|
the host information is retrieved from the host database file, no conversion is
|
||
|
|
done on the host name specified by the <em>host_name</em> parameter unless the
|
||
|
|
CCSID of the job is something other than 65535. In addition, the host names
|
||
|
|
returned in the hostent structure will be returned in the default CCSID of the
|
||
|
|
job if they are obtained from the domain name server. For translation to occur
|
||
|
|
for the host names returned in the hostent structure when they are obtained
|
||
|
|
from the host database file, you must use a job CCSID of something other than
|
||
|
|
65535.</p>
|
||
|
|
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>Address families are defined in <strong><sys/socket.h></strong>, and
|
||
|
|
the <strong>in_addr</strong> structure is defined in
|
||
|
|
<strong><netinet/in.h></strong>.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>Do not use the <em>gethostbyname()</em> function in a multithreaded
|
||
|
|
environment. See the multithread alternative <em>gethostbyname_r()</em>
|
||
|
|
function.<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><em>gethostbyname()</em> will resolve local host aliases to a domain name
|
||
|
|
which are then resolved with a query using DNS. See <a href=
|
||
|
|
"reshostalias.htm">res_hostalias()</a> for more information on aliases. <br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li>When you develop in C-based languages and an application is compiled with the _XOPEN_SOURCE
|
||
|
|
macro defined to the value 520 or greater, the <em>gethostbyname()</em> API is mapped to
|
||
|
|
<em>qso_gethostbyname98()</em>.</li>
|
||
|
|
</ol>
|
||
|
|
|
||
|
|
<br>
|
||
|
|
|
||
|
|
|
||
|
|
<h3>Related Information</h3>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li><a href="_xopen_source.htm">_XOPEN_SOURCE</a>--Using _XOPEN_SOURCE for the UNIX 98
|
||
|
|
compatible interface<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="hstrerror.htm">hstrerror()</a>--Retrieve Resolver Error
|
||
|
|
Message<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="reshostalias.htm">res_hostalias()</a>--Retrieve the host alias<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="ghosta.htm">gethostbyaddr()</a>--Get Host Information for IP
|
||
|
|
Address<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="ghostnt.htm">gethostent()</a>--Get Next Entry from Host
|
||
|
|
Database<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="shostnt.htm">sethostent()</a>--Open Host Database<br>
|
||
|
|
<br>
|
||
|
|
</li>
|
||
|
|
|
||
|
|
<li><a href="ehostnt.htm">endhostent()</a>--Close Host Database</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>
|
||
|
|
|