📄 getnameinfo.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>getnameinfo</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="getnameinfo"></a> <a name="tag_03_232"></a><!-- getnameinfo --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_232_01"></a>NAME</h4><blockquote>getnameinfo - get name information</blockquote><h4><a name="tag_03_232_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/sys/socket.h.html">sys/socket.h</a>><br> #include <<a href="../basedefs/netdb.h.html">netdb.h</a>><br><br> int getnameinfo(const struct sockaddr *restrict</tt> <i>sa</i><tt>, socklen_t</tt> <i>salen</i><tt>,<br> char *restrict</tt> <i>node</i><tt>, socklen_t</tt> <i>nodelen</i><tt>, char *restrict</tt><i>service</i><tt>,<br> socklen_t</tt> <i>servicelen</i><tt>, int</tt> <i>flags</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_232_03"></a>DESCRIPTION</h4><blockquote><p>The <i>getnameinfo</i>() function shall translate a socket address to a node name and service location, all of which are definedas in <a href="getaddrinfo.html"><i>getaddrinfo</i>()</a> .</p><p>The <i>sa</i> argument points to a socket address structure to be translated.</p><p><sup>[<a href="javascript:open_code('IP6')">IP6</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">If the socket address structure contains an IPv4-mapped IPv6 address or an IPv4-compatible IPv6 address, the implementation shallextract the embedded IPv4 address and lookup the node name for that IPv4 address. <img src="../images/opt-end.gif" alt="[Option End]" border="0"> <basefont size="2"></p><dl><dt><b>Note:</b></dt><dd>The IPv6 unspecified address ( <tt>"::"</tt> ) and the IPv6 loopback address ( <tt>"::1"</tt> ) are not IPv4-compatibleaddresses. If the address is the IPv6 unspecified address ( <tt>"::"</tt> ), a lookup is not performed, and the [EAI_NONAME] erroris returned.</dd></dl><basefont size="3"> <p>If the <i>node</i> argument is non-NULL and the <i>nodelen</i> argument is non-zero, then the <i>node</i> argument points to abuffer able to contain up to <i>nodelen</i> characters that receives the node name as a null-terminated string. If the <i>node</i>argument is NULL or the <i>nodelen</i> argument is zero, the node name shall not be returned. If the node's name cannot be located,the numeric form of the address contained in the socket address structure pointed to by the <i>sa</i> argument is returned insteadof its name.</p><p>If the <i>service</i> argument is non-NULL and the <i>servicelen</i> argument is non-zero, then the <i>service</i> argumentpoints to a buffer able to contain up to <i>servicelen</i> bytes that receives the service name as a null-terminated string. If the<i>service</i> argument is NULL or the <i>servicelen</i> argument is zero, the service name shall not be returned. If the service'sname cannot be located, the numeric form of the service address (for example, its port number) shall be returned instead of itsname.</p><p>The <i>flags</i> argument is a flag that changes the default actions of the function. By default the fully-qualified domain name(FQDN) for the host shall be returned, but:</p><ul><li><p>If the flag bit NI_NOFQDN is set, only the node name portion of the FQDN shall be returned for local hosts.</p></li><li><p>If the flag bit NI_NUMERICHOST is set, the numeric form of the address contained in the socket address structure pointed to bythe <i>sa</i> argument shall be returned instead of its name, under all circumstances.</p></li><li><p>If the flag bit NI_NAMEREQD is set, an error shall be returned if the host's name cannot be located.</p></li><li><p>If the flag bit NI_NUMERICSERV is set, the numeric form of the service address shall be returned (for example, its port number)instead of its name, under all circumstances.</p></li><li><p>If the flag bit NI_NUMERICSCOPE is set, the numeric form of the scope identifier shall be returned (for example, interfaceindex) instead of its name. This flag shall be ignored if the <i>sa</i> argument is not an IPv6 address.</p></li><li><p>If the flag bit NI_DGRAM is set, this indicates that the service is a datagram service (SOCK_DGRAM). The default behavior shallassume that the service is a stream service (SOCK_STREAM).</p></li></ul><basefont size="2"> <dl><dt><b>Notes:</b></dt><dd><ol><li><p>The two NI_NUMERICxxx flags are required to support the <b>-n</b> flag that many commands provide.</p></li><li><p>The NI_DGRAM flag is required for the few AF_INET and AF_INET6 port numbers (for example, [512,514]) that represent differentservices for UDP and TCP.</p></li></ol></dd></dl><basefont size="3"> <p>The <i>getnameinfo</i>() function shall be thread-safe.</p></blockquote><h4><a name="tag_03_232_04"></a>RETURN VALUE</h4><blockquote><p>A zero return value for <i>getnameinfo</i>() indicates successful completion; a non-zero return value indicates failure. Thepossible values for the failures are listed in the ERRORS section.</p><p>Upon successful completion, <i>getnameinfo</i>() shall return the <i>node</i> and <i>service</i> names, if requested, in thebuffers provided. The returned names are always null-terminated strings.</p></blockquote><h4><a name="tag_03_232_05"></a>ERRORS</h4><blockquote><p>The <i>getnameinfo</i>() function shall fail and return the corresponding value if:</p><dl compact><dt>[EAI_AGAIN]</dt><dd>The name could not be resolved at this time. Future attempts may succeed.</dd><dt>[EAI_BADFLAGS]</dt><dd><br>The <i>flags</i> had an invalid value.</dd><dt>[EAI_FAIL]</dt><dd>A non-recoverable error occurred.</dd><dt>[EAI_FAMILY]</dt><dd>The address family was not recognized or the address length was invalid for the specified family.</dd><dt>[EAI_MEMORY]</dt><dd>There was a memory allocation failure.</dd><dt>[EAI_NONAME]</dt><dd>The name does not resolve for the supplied parameters. <p>NI_NAMEREQD is set and the host's name cannot be located, or both <i>nodename</i> and <i>servname</i> were null.</p></dd><dt>[EAI_OVERFLOW]</dt><dd><br>An argument buffer overflowed. The buffer pointed to by the <i>node</i> argument or the <i>service</i> argument was too small.</dd><dt>[EAI_SYSTEM]</dt><dd>A system error occurred. The error code can be found in <i>errno</i>.</dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_232_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_232_07"></a>APPLICATION USAGE</h4><blockquote><p>If the returned values are to be used as part of any further name resolution (for example, passed to <a href="../functions/getaddrinfo.html"><i>getaddrinfo</i>()</a>), applications should provide buffers large enough to store any resultpossible on the system.</p><p>Given the IPv4-mapped IPv6 address <tt>"::ffff:1.2.3.4"</tt> , the implementation performs a lookup as if the socket addressstructure contains the IPv4 address <tt>"1.2.3.4"</tt> .</p></blockquote><h4><a name="tag_03_232_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_232_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_232_10"></a>SEE ALSO</h4><blockquote><p><a href="gai_strerror.html"><i>gai_strerror</i>()</a> , <a href="getaddrinfo.html"><i>getaddrinfo</i>()</a> , <a href="getservbyname.html"><i>getservbyname</i>()</a> , <a href="inet_ntop.html"><i>inet_ntop</i>()</a> , <a href="socket.html"><i>socket</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/netdb.h.html"><i><netdb.h></i></a>, <a href="../basedefs/sys/socket.h.html"><i><sys/socket.h></i></a></p></blockquote><h4><a name="tag_03_232_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 6. Derived from the XNS, Issue 5.2 specification.</p><p>The <b>restrict</b> keyword is added to the <i>getnameinfo</i>() prototype for alignment with the ISO/IEC 9899:1999standard.</p><p>IEEE Std 1003.1-2001/Cor 1-2002, item XSH/TC1/D6/23 is applied, making various changes in the SYNOPSIS and DESCRIPTIONfor alignment with IPv6.</p><p>IEEE Std 1003.1-2001/Cor 1-2002, item XSH/TC1/D6/24 is applied, adding the [EAI_OVERFLOW] error to the ERRORSsection.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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