208 lines
8.4 KiB
HTML
208 lines
8.4 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>asctime</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="asctime"></a> <a name="tag_03_22"></a><!-- asctime -->
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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_22_01"></a>NAME</h4>
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<blockquote>asctime, asctime_r - convert date and time to a string</blockquote>
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<h4><a name="tag_03_22_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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char *asctime(const struct tm *</tt><i>timeptr</i><tt>);<br>
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</tt></code></p>
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> char *asctime_r(const struct tm *restrict</tt> <i>tm</i><tt>, char *restrict</tt> <i>buf</i><tt>);
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<img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_22_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>For <i>asctime</i>(): <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any
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conflict between the requirements described here and the ISO C standard is unintentional. This volume of
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IEEE Std 1003.1-2001 defers to the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border=
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"0"></p>
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<p>The <i>asctime</i>() function shall convert the broken-down time in the structure pointed to by <i>timeptr</i> into a string in
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the form:</p>
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<pre>
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<tt>Sun Sep 16 01:03:52 1973\n\0
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</tt>
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</pre>
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<p>using the equivalent of the following algorithm:</p>
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<pre>
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<tt>char *asctime(const struct tm *timeptr)
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{
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static char wday_name[7][3] = {
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"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
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};
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static char mon_name[12][3] = {
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"Jan", "Feb", "Mar", "Apr", "May", "Jun",
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"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
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};
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static char result[26];
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<br>
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sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
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wday_name[timeptr->tm_wday],
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mon_name[timeptr->tm_mon],
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timeptr->tm_mday, timeptr->tm_hour,
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timeptr->tm_min, timeptr->tm_sec,
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1900 + timeptr->tm_year);
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return result;
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}
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</tt>
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</pre>
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<p>The <b>tm</b> structure is defined in the <a href="../basedefs/time.h.html"><i><time.h></i></a> header.</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"> The
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<i>asctime</i>(), <a href="../functions/ctime.html"><i>ctime</i>()</a>, <a href="../functions/gmtime.html"><i>gmtime</i>()</a>, and
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<a href="../functions/localtime.html"><i>localtime</i>()</a> functions shall return values in one of two static objects: a
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broken-down time structure and an array of type <b>char</b>. Execution of any of the functions may overwrite the information
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returned in either of these objects by any of the other functions.</p>
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<p>The <i>asctime</i>() function need not be reentrant. A function that is not required to be reentrant is not required to be
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thread-safe. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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<p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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The <i>asctime_r</i>() function shall convert the broken-down time in the structure pointed to by <i>tm</i> into a string (of the
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same form as that returned by <i>asctime</i>()) that is placed in the user-supplied buffer pointed to by <i>buf</i> (which shall
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contain at least 26 bytes) and then return <i>buf</i>. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_03_22_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, <i>asctime</i>() shall return a pointer to the string.</p>
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<p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Upon successful completion, <i>asctime_r</i>() shall return a pointer to a character string containing the date and time. This
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string is pointed to by the argument <i>buf</i>. If the function is unsuccessful, it shall return NULL. <img src=
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"../images/opt-end.gif" alt="[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_03_22_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_22_06"></a>EXAMPLES</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_22_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>Values for the broken-down time structure can be obtained by calling <a href="../functions/gmtime.html"><i>gmtime</i>()</a> or
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<a href="../functions/localtime.html"><i>localtime</i>()</a>. This function is included for compatibility with older
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implementations, and does not support localized date and time formats. Applications should use <a href=
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"../functions/strftime.html"><i>strftime</i>()</a> to achieve maximum portability.</p>
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<p>The <i>asctime_r</i>() function is thread-safe and shall return values in a user-supplied buffer instead of possibly using a
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static data area that may be overwritten by each call.</p>
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</blockquote>
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<h4><a name="tag_03_22_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_22_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_22_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="clock.html"><i>clock</i>()</a> , <a href="ctime.html"><i>ctime</i>()</a> , <a href=
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"difftime.html"><i>difftime</i>()</a> , <a href="gmtime.html"><i>gmtime</i>()</a> , <a href="localtime.html"><i>localtime</i>()</a>
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, <a href="mktime.html"><i>mktime</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_22_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 1. Derived from Issue 1 of the SVID.</p>
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</blockquote>
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<h4><a name="tag_03_22_12"></a>Issue 5</h4>
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<blockquote>
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<p>Normative text previously in the APPLICATION USAGE section is moved to the DESCRIPTION.</p>
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<p>The <i>asctime_r</i>() function is included for alignment with the POSIX Threads Extension.</p>
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<p>A note indicating that the <i>asctime</i>() function need not be reentrant is added to the DESCRIPTION.</p>
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</blockquote>
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<h4><a name="tag_03_22_13"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>asctime_r</i>() function is marked as part of the Thread-Safe Functions option.</p>
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<p>Extensions beyond the ISO C standard are marked.</p>
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<p>The APPLICATION USAGE section is updated to include a note on the thread-safe function and its avoidance of possibly using a
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static data area.</p>
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<p>The DESCRIPTION of <i>asctime_r</i>() is updated to describe the format of the string returned.</p>
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<p>The <b>restrict</b> keyword is added to the <i>asctime_r</i>() prototype for alignment with the ISO/IEC 9899:1999
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standard.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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<hr>
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<center><font size="2"><!--footer start-->
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UNIX ® is a registered Trademark of The Open Group.<br>
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POSIX ® is a registered Trademark of The IEEE.<br>
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[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href=
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