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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) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>atoi</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="atoi"></a> <a name="tag_03_34"></a><!-- atoi --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_34_01"></a>NAME</h4><blockquote>atoi - convert a string to an integer</blockquote><h4><a name="tag_03_34_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/stdlib.h.html">stdlib.h</a>><br><br> int atoi(const char *</tt><i>str</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_34_03"></a>DESCRIPTION</h4><blockquote><div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between therequirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers tothe ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div><p>The call <i>atoi</i>(<i>str</i>) shall be equivalent to:</p><pre><tt>(int) strtol(str, (char **)NULL, 10)</tt></pre><p>except that the handling of errors may differ. If the value cannot be represented, the behavior is undefined.</p></blockquote><h4><a name="tag_03_34_04"></a>RETURN VALUE</h4><blockquote><p>The <i>atoi</i>() function shall return the converted value if the value can be represented.</p></blockquote><h4><a name="tag_03_34_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_34_06"></a>EXAMPLES</h4><blockquote><h5><a name="tag_03_34_06_01"></a>Converting an Argument</h5><p>The following example checks for proper usage of the program. If there is an argument and the decimal conversion of thisargument (obtained using <i>atoi</i>()) is greater than 0, then the program has a valid number of minutes to wait for an event.</p><pre><tt>#include <stdlib.h>#include <stdio.h>...int minutes_to_event;...if (argc < 2 || ((minutes_to_event = atoi (argv[1]))) <= 0) { fprintf(stderr, "Usage: %s minutes\n", argv[0]); exit(1);}...</tt></pre></blockquote><h4><a name="tag_03_34_07"></a>APPLICATION USAGE</h4><blockquote><p>The <i>atoi</i>() function is subsumed by <a href="../functions/strtol.html"><i>strtol</i>()</a> but is retained because it isused extensively in existing code. If the number is not known to be in range, <a href="../functions/strtol.html"><i>strtol</i>()</a> should be used because <i>atoi</i>() is not required to perform any errorchecking.</p></blockquote><h4><a name="tag_03_34_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_34_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_34_10"></a>SEE ALSO</h4><blockquote><p><a href="strtol.html"><i>strtol</i>()</a>, the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/stdlib.h.html"><i><stdlib.h></i></a></p></blockquote><h4><a name="tag_03_34_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><div class="box"><em>End of informative text.</em></div><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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