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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>inet_addr</title></head><body bgcolor="white"><basefont size="3"> <a name="inet_addr"></a> <a name="tag_03_278"></a><!-- inet_addr --> <!--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_278_01"></a>NAME</h4><blockquote>inet_addr, inet_ntoa - IPv4 address manipulation</blockquote><h4><a name="tag_03_278_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/arpa/inet.h.html">arpa/inet.h</a>><br><br> in_addr_t inet_addr(const char *</tt><i>cp</i><tt>);<br> char *inet_ntoa(struct in_addr</tt> <i>in</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_278_03"></a>DESCRIPTION</h4><blockquote><p>The <i>inet_addr</i>() function shall convert the string pointed to by <i>cp</i>, in the standard IPv4 dotted decimal notation,to an integer value suitable for use as an Internet address.</p><p>The <i>inet_ntoa</i>() function shall convert the Internet host address specified by <i>in</i> to a string in the Internetstandard dot notation.</p><p>The <i>inet_ntoa</i>() function need not be reentrant. A function that is not required to be reentrant is not required to bethread-safe.</p><p>All Internet addresses shall be returned in network order (bytes ordered from left to right).</p><p>Values specified using IPv4 dotted decimal notation take one of the following forms:</p><dl compact><dt><tt>a.b.c.d</tt></dt><dd>When four parts are specified, each shall be interpreted as a byte of data and assigned, from left to right, to the four bytesof an Internet address.</dd><dt><tt>a.b.c</tt></dt><dd>When a three-part address is specified, the last part shall be interpreted as a 16-bit quantity and placed in the rightmost twobytes of the network address. This makes the three-part address format convenient for specifying Class B network addresses as<tt>"128.net.host"</tt> .</dd><dt><tt>a.b</tt></dt><dd>When a two-part address is supplied, the last part shall be interpreted as a 24-bit quantity and placed in the rightmost threebytes of the network address. This makes the two-part address format convenient for specifying Class A network addresses as<tt>"net.host"</tt> .</dd><dt><tt>a</tt></dt><dd>When only one part is given, the value shall be stored directly in the network address without any byte rearrangement.</dd></dl><p>All numbers supplied as parts in IPv4 dotted decimal notation may be decimal, octal, or hexadecimal, as specified in theISO C standard (that is, a leading 0x or 0X implies hexadecimal; otherwise, a leading <tt>'0'</tt> implies octal; otherwise,the number is interpreted as decimal).</p></blockquote><h4><a name="tag_03_278_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>inet_addr</i>() shall return the Internet address. Otherwise, it shall return (<b>in_addr_t</b>)(-1).</p><p>The <i>inet_ntoa</i>() function shall return a pointer to the network address in Internet standard dot notation.</p></blockquote><h4><a name="tag_03_278_05"></a>ERRORS</h4><blockquote><p>No errors are defined.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_278_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_278_07"></a>APPLICATION USAGE</h4><blockquote><p>The return value of <i>inet_ntoa</i>() may point to static data that may be overwritten by subsequent calls to<i>inet_ntoa</i>().</p></blockquote><h4><a name="tag_03_278_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_278_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_278_10"></a>SEE ALSO</h4><blockquote><p><a href="endhostent.html"><i>endhostent</i>()</a> , <a href="endnetent.html"><i>endnetent</i>()</a> , the Base Definitionsvolume of IEEE Std 1003.1-2001, <a href="../basedefs/arpa/inet.h.html"><i><arpa/inet.h></i></a></p></blockquote><h4><a name="tag_03_278_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 6. Derived from the XNS, Issue 5.2 specification.</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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