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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>gmtime</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="gmtime"></a> <a name="tag_03_261"></a><!-- gmtime --> <!--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_261_01"></a>NAME</h4><blockquote>gmtime, gmtime_r - convert a time value to a broken-down UTC time</blockquote><h4><a name="tag_03_261_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/time.h.html">time.h</a>><br><br> struct tm *gmtime(const time_t *</tt><i>timer</i><tt>);<br></tt></code></p><div class="box"><code><tt><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> struct tm *gmtime_r(const time_t *restrict</tt> <i>timer</i><tt>,<br> struct tm *restrict</tt> <i>result</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_261_03"></a>DESCRIPTION</h4><blockquote><p>For <i>gmtime</i>(): <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. Anyconflict between the requirements described here and the ISO C standard is unintentional. This volume ofIEEE Std 1003.1-2001 defers to the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p>The <i>gmtime</i>() function shall convert the time in seconds since the Epoch pointed to by <i>timer</i> into a broken-downtime, expressed as Coordinated Universal Time (UTC).</p><p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> Therelationship between a time in seconds since the Epoch used as an argument to <i>gmtime</i>() and the <b>tm</b> structure (definedin the <a href="../basedefs/time.h.html"><i><time.h></i></a> header) is that the result shall be as specified in theexpression given in the definition of 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>), where the names in the structure and inthe expression correspond. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The same relationship shall apply for <i>gmtime_r</i>(). <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> The<i>gmtime</i>() function need not be reentrant. A function that is not required to be reentrant is not required to bethread-safe.</p><p>The <a href="../functions/asctime.html"><i>asctime</i>()</a>, <a href="../functions/ctime.html"><i>ctime</i>()</a>,<i>gmtime</i>(), and <a href="../functions/localtime.html"><i>localtime</i>()</a> functions shall return values in one of twostatic objects: a broken-down time structure and an array of type <b>char</b>. Execution of any of the functions may overwrite theinformation returned in either of these objects by any of the other functions. <img src="../images/opt-end.gif" alt="[Option End]"border="0"></p><p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The <i>gmtime_r</i>() function shall convert the time in seconds since the Epoch pointed to by <i>timer</i> into a broken-down timeexpressed as Coordinated Universal Time (UTC). The broken-down time is stored in the structure referred to by <i>result</i>. The<i>gmtime_r</i>() function shall also return the address of the same structure. <img src="../images/opt-end.gif" alt="[Option End]"border="0"></p></blockquote><h4><a name="tag_03_261_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, the <i>gmtime</i>() function shall return a pointer to a <b>struct tm</b>. If an error is detected,<i>gmtime</i>() shall return a null pointer <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and set <i>errno</i> to indicate the error. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Upon successful completion, <i>gmtime_r</i>() shall return the address of the structure pointed to by the argument <i>result</i>.If an error is detected, <i>gmtime_r</i>() shall return a null pointer and 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_261_05"></a>ERRORS</h4><blockquote><p>The <i>gmtime</i>() <sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and <i>gmtime_r</i>() <img src="../images/opt-end.gif" alt="[Option End]" border="0"> functions shall 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_261_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_261_07"></a>APPLICATION USAGE</h4><blockquote><p>The <i>gmtime_r</i>() function is thread-safe and returns values in a user-supplied buffer instead of possibly using a staticdata area that may be overwritten by each call.</p></blockquote><h4><a name="tag_03_261_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_261_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_261_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="localtime.html"><i>localtime</i>()</a>, <a href="mktime.html"><i>mktime</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="utime.html"><i>utime</i>()</a>, the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/time.h.html"><i><time.h></i></a></p></blockquote><h4><a name="tag_03_261_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</p></blockquote><h4><a name="tag_03_261_12"></a>Issue 5</h4><blockquote><p>A note indicating that the <i>gmtime</i>() function need not be reentrant is added to the DESCRIPTION.</p><p>The <i>gmtime_r</i>() function is included for alignment with the POSIX Threads Extension.</p></blockquote><h4><a name="tag_03_261_13"></a>Issue 6</h4><blockquote><p>The <i>gmtime_r</i>() function is marked as part of the Thread-Safe Functions option.</p><p>Extensions beyond the ISO C standard are marked.</p><p>The APPLICATION USAGE section is updated to include a note on the thread-safe function and its avoidance of possibly using astatic data area.</p><p>The <b>restrict</b> keyword is added to the <i>gmtime_r</i>() prototype for alignment with the ISO/IEC 9899:1999standard.</p><p>IEEE Std 1003.1-2001/Cor 1-2002, item XSH/TC1/D6/27 is applied, adding the [EOVERFLOW] error.</p><p>IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/48 is applied, updating the error handling for<i>gmtime_r</i>().</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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