📄 ctime.html
字号:
<!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>ctime</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="ctime"></a> <a name="tag_03_103"></a><!-- ctime --> <!--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_103_01"></a>NAME</h4><blockquote>ctime, ctime_r - convert a time value to a date and time string</blockquote><h4><a name="tag_03_103_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/time.h.html">time.h</a>><br><br> char *ctime(const time_t *</tt><i>clock</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"> char *ctime_r(const time_t *</tt><i>clock</i><tt>, char *</tt><i>buf</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_103_03"></a>DESCRIPTION</h4><blockquote><p>For <i>ctime</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>ctime</i>() function shall convert the time pointed to by <i>clock</i>, representing time in seconds since the Epoch, tolocal time in the form of a string. It shall be equivalent to:</p><pre><tt>asctime(localtime(clock))</tt></pre><p><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> The<a href="../functions/asctime.html"><i>asctime</i>()</a>, <i>ctime</i>(), <a href="../functions/gmtime.html"><i>gmtime</i>()</a>,and <a href="../functions/localtime.html"><i>localtime</i>()</a> functions shall return values in one of two static objects: abroken-down time structure and an array of <b>char</b>. Execution of any of the functions may overwrite the information returned ineither of these objects by any of the other functions.</p><p>The <i>ctime</i>() function need not be reentrant. A function that is not required to be reentrant is not required to bethread-safe. <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>ctime_r</i>() function shall convert the calendar time pointed to by <i>clock</i> to local time in exactly the same form as<i>ctime</i>() and put the string into the array pointed to by <i>buf</i> (which shall be at least 26 bytes in size) and return<i>buf</i>.</p><p>Unlike <i>ctime</i>(), the thread-safe version <i>ctime_r</i>() is not required to set <i>tzname</i>. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_103_04"></a>RETURN VALUE</h4><blockquote><p>The <i>ctime</i>() function shall return the pointer returned by <a href="../functions/asctime.html"><i>asctime</i>()</a> withthat broken-down time as an argument.</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>ctime_r</i>() shall return a pointer to the string pointed to by <i>buf</i>. When an error isencountered, a null pointer shall be returned. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_103_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_103_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_103_07"></a>APPLICATION USAGE</h4><blockquote><p>Values for the broken-down time structure can be obtained by calling <a href="../functions/gmtime.html"><i>gmtime</i>()</a> or<a href="../functions/localtime.html"><i>localtime</i>()</a>. The <i>ctime</i>() function is included for compatibility with olderimplementations, and does not support localized date and time formats. Applications should use the <a href="../functions/strftime.html"><i>strftime</i>()</a> function to achieve maximum portability.</p><p>The <i>ctime_r</i>() function is thread-safe and shall return values in a user-supplied buffer instead of possibly using astatic data area that may be overwritten by each call.</p></blockquote><h4><a name="tag_03_103_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_103_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_103_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="difftime.html"><i>difftime</i>()</a> , <a href="gmtime.html"><i>gmtime</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 BaseDefinitions 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_103_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_103_12"></a>Issue 5</h4><blockquote><p>Normative text previously in the APPLICATION USAGE section is moved to the DESCRIPTION.</p><p>The <i>ctime_r</i>() function is included for alignment with the POSIX Threads Extension.</p><p>A note indicating that the <i>ctime</i>() function need not be reentrant is added to the DESCRIPTION.</p></blockquote><h4><a name="tag_03_103_13"></a>Issue 6</h4><blockquote><p>Extensions beyond the ISO C standard are marked.</p><p>In the DESCRIPTION, the note about reentrancy is expanded to cover thread-safety.</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></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
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -