176 lines
6.9 KiB
HTML
176 lines
6.9 KiB
HTML
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<link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 -->
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>mktime</title>
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<body bgcolor="white">
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<script type="text/javascript" language="JavaScript" src="../jscript/codes.js">
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<basefont size="3"> <a name="mktime"></a> <a name="tag_03_376"></a><!-- mktime -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_376_01"></a>NAME</h4>
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<blockquote>mktime - convert broken-down time into time since the Epoch</blockquote>
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<h4><a name="tag_03_376_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/time.h.html">time.h</a>><br>
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<br>
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time_t mktime(struct tm *</tt><i>timeptr</i><tt>);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_376_03"></a>DESCRIPTION</h4>
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<blockquote>
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<div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"
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border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
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requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to
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the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div>
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<p>The <i>mktime</i>() function shall convert the broken-down time, expressed as local time, in the structure pointed to by
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<i>timeptr</i>, into a time since the Epoch value with the same encoding as that of the values returned by <a href=
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"../functions/time.html"><i>time</i>()</a>. The original values of the <i>tm_wday</i> and <i>tm_yday</i> components of the
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structure are ignored, and the original values of the other components are not restricted to the ranges described in <a href=
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"../basedefs/time.h.html"><i><time.h></i></a>.</p>
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<p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> A
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positive or 0 value for <i>tm_isdst</i> shall cause <i>mktime</i>() to presume initially that Daylight Savings Time, respectively,
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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 to
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determine whether Daylight Savings Time is in effect for the specified time.</p>
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<p>Local timezone information shall be set as though <i>mktime</i>() called <a href=
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"../functions/tzset.html"><i>tzset</i>()</a>.</p>
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<p>The relationship between the <b>tm</b> structure (defined in the <a href="../basedefs/time.h.html"><i><time.h></i></a>
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header) and the time in seconds since the Epoch is that the result shall be as specified in the expression given in the definition
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of seconds since the Epoch (see the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/xbd_chap04.html#tag_04_14">Section 4.14, Seconds Since the Epoch</a>) corrected for timezone and any seasonal time
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adjustments, where the names in the structure and in the expression correspond. <img src="../images/opt-end.gif" alt="[Option End]"
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border="0"></p>
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<p>Upon successful completion, the values of the <i>tm_wday</i> and <i>tm_yday</i> components of the structure shall be set
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appropriately, and the other components are set to represent the specified time since the Epoch, but with their values forced to
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the ranges indicated in the <a href="../basedefs/time.h.html"><i><time.h></i></a> entry; the final value of <i>tm_mday</i>
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shall not be set until <i>tm_mon</i> and <i>tm_year</i> are determined.</p>
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</blockquote>
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<h4><a name="tag_03_376_04"></a>RETURN VALUE</h4>
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<blockquote>
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<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 the
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time since the Epoch cannot be represented, the function shall return the value (<b>time_t</b>)-1.</p>
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</blockquote>
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<h4><a name="tag_03_376_05"></a>ERRORS</h4>
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<blockquote>
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<p>No errors are defined.</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_376_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>What day of the week is July 4, 2001?</p>
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<pre>
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<tt>#include <stdio.h>
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#include <time.h>
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<br>
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struct tm time_str;
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<br>
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char daybuf[20];
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<br>
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int main(void)
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{
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time_str.tm_year = 2001 - 1900;
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time_str.tm_mon = 7 - 1;
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time_str.tm_mday = 4;
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time_str.tm_hour = 0;
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time_str.tm_min = 0;
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time_str.tm_sec = 1;
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time_str.tm_isdst = -1;
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if (mktime(&time_str) == -1)
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(void)puts("-unknown-");
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else {
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(void)strftime(daybuf, sizeof(daybuf), "%A", &time_str);
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(void)puts(daybuf);
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}
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return 0;
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}
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</tt>
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</pre>
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</blockquote>
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<h4><a name="tag_03_376_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_376_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_376_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_376_10"></a>SEE ALSO</h4>
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<blockquote>
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<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>
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, <a href="difftime.html"><i>difftime</i>()</a> , <a href="gmtime.html"><i>gmtime</i>()</a> , <a href=
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"localtime.html"><i>localtime</i>()</a> , <a href="strftime.html"><i>strftime</i>()</a> , <a href=
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"strptime.html"><i>strptime</i>()</a> , <a href="time.html"><i>time</i>()</a> , <a href="utime.html"><i>utime</i>()</a> , the Base
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Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/time.h.html"><i><time.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_376_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 3. Included for alignment with the POSIX.1-1988 standard and the ANSI C standard.</p>
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</blockquote>
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<h4><a name="tag_03_376_12"></a>Issue 6</h4>
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<blockquote>
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<p>Extensions beyond the ISO C standard are marked.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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