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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>mktime</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="mktime"></a> <a name="tag_03_376"></a><!-- mktime --> <!--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_376_01"></a>NAME</h4><blockquote>mktime - convert broken-down time into time since the Epoch</blockquote><h4><a name="tag_03_376_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/time.h.html">time.h</a>><br><br> time_t mktime(struct tm *</tt><i>timeptr</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_376_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 <i>mktime</i>() function shall convert the broken-down time, expressed as local time, in the structure pointed to by<i>timeptr</i>, into a time since the Epoch value with the same encoding as that of the values returned by <a href="../functions/time.html"><i>time</i>()</a>. The original values of the <i>tm_wday</i> and <i>tm_yday</i> components of thestructure are ignored, and the original values of the other components are not restricted to the ranges described in <a href="../basedefs/time.h.html"><i><time.h></i></a>.</p><p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> Apositive or 0 value for <i>tm_isdst</i> shall cause <i>mktime</i>() to presume initially that Daylight Savings Time, respectively,is or is not in effect for the specified time. A negative value for <i>tm_isdst</i> shall cause <i>mktime</i>() to attempt todetermine whether Daylight Savings Time is in effect for the specified time.</p><p>Local timezone information shall be set as though <i>mktime</i>() called <a href="../functions/tzset.html"><i>tzset</i>()</a>.</p><p>The relationship between the <b>tm</b> structure (defined in the <a href="../basedefs/time.h.html"><i><time.h></i></a>header) and the time in seconds since the Epoch is that the result shall be as specified in the expression given in the definitionof seconds since the Epoch (see the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap04.html#tag_04_14">Section 4.14, Seconds Since the Epoch</a>) corrected for timezone and any seasonal timeadjustments, where the names in the structure and in the expression correspond. <img src="../images/opt-end.gif" alt="[Option End]"border="0"></p><p>Upon successful completion, the values of the <i>tm_wday</i> and <i>tm_yday</i> components of the structure shall be setappropriately, and the other components are set to represent the specified time since the Epoch, but with their values forced tothe ranges indicated in the <a href="../basedefs/time.h.html"><i><time.h></i></a> entry; the final value of <i>tm_mday</i>shall not be set until <i>tm_mon</i> and <i>tm_year</i> are determined.</p></blockquote><h4><a name="tag_03_376_04"></a>RETURN VALUE</h4><blockquote><p>The <i>mktime</i>() function shall return the specified time since the Epoch encoded as a value of type <b>time_t</b>. If thetime since the Epoch cannot be represented, the function shall return the value (<b>time_t</b>)-1 <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and may set<i>errno</i> to indicate the error. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_376_05"></a>ERRORS</h4><blockquote><p>The <i>mktime</i>() function may fail if:</p><dl compact><dt>[EOVERFLOW]</dt><dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The result cannot be represented. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_376_06"></a>EXAMPLES</h4><blockquote><p>What day of the week is July 4, 2001?</p><pre><tt>#include <stdio.h>#include <time.h><br>struct tm time_str;<br>char daybuf[20];<br>int main(void){ time_str.tm_year = 2001 - 1900; time_str.tm_mon = 7 - 1; time_str.tm_mday = 4; time_str.tm_hour = 0; time_str.tm_min = 0; time_str.tm_sec = 1; time_str.tm_isdst = -1; if (mktime(&time_str) == -1) (void)puts("-unknown-"); else { (void)strftime(daybuf, sizeof(daybuf), "%A", &time_str); (void)puts(daybuf); } return 0;}</tt></pre></blockquote><h4><a name="tag_03_376_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_376_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_376_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_376_10"></a>SEE ALSO</h4><blockquote><p><a href="asctime.html"><i>asctime</i>()</a>, <a href="clock.html"><i>clock</i>()</a>, <a href="ctime.html"><i>ctime</i>()</a>, <a href="difftime.html"><i>difftime</i>()</a>, <a href="gmtime.html"><i>gmtime</i>()</a>, <a href="localtime.html"><i>localtime</i>()</a>, <a href="strftime.html"><i>strftime</i>()</a>, <a href="strptime.html"><i>strptime</i>()</a>, <a href="time.html"><i>time</i>()</a>, <a href="tzset.html"><i>tzset</i>()</a>, <a href="utime.html"><i>utime</i>()</a>, the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/time.h.html"><i><time.h></i></a></p></blockquote><h4><a name="tag_03_376_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 3. Included for alignment with the POSIX.1-1988 standard and the ANSI C standard.</p></blockquote><h4><a name="tag_03_376_12"></a>Issue 6</h4><blockquote><p>Extensions beyond the ISO C standard are marked.</p><p>IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/58 is applied, updating the RETURN VALUE and ERRORS sections toadd the optional [EOVERFLOW] error as a CX extension.</p><p>IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/59 is applied, adding the <a href="../functions/tzset.html"><i>tzset</i>()</a> function to the SEE ALSO section.</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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