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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>asctime</title></head><body bgcolor=white><center><font size=2>The Single UNIX ® Specification, Version 2<br>Copyright © 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_000_001_176"> </a>NAME</h4><blockquote>asctime, asctime_r - convert date and time to a string</blockquote><h4><a name = "tag_000_001_177"> </a>SYNOPSIS</h4><blockquote><pre><code>#include <<a href="time.h.html">time.h</a>>char *asctime(const struct tm *<i>timeptr</i>);char *asctime_r(const struct tm *<i>tm</i>, char *<i>buf</i>);</code></pre></blockquote><h4><a name = "tag_000_001_178"> </a>DESCRIPTION</h4><blockquote>The<i>asctime()</i>function converts the broken-down time in the structure pointedto by<i>timeptr</i>into a string in the form:<pre><code>Sun Sep 16 01:03:52 1973\n\0</code></pre>using the equivalent of the following algorithm:<pre><code>char *asctime(const struct tm *timeptr){ static char wday_name[7][3] = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" }; static char mon_name[12][3] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" }; static char result[26]; sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n", wday_name[timeptr->tm_wday], mon_name[timeptr->tm_mon], timeptr->tm_mday, timeptr->tm_hour, timeptr->tm_min, timeptr->tm_sec, 1900 + timeptr->tm_year); return result;}</code></pre><p>The <b>tm</b> structure is defined in the<i><a href="time.h.html"><time.h></a></i>header.<p>The<i>asctime()</i>,<i><a href="ctime.html">ctime()</a></i>,<i><a href="gmtime.html">gmtime()</a></i>and<i><a href="localtime.html">localtime()</a></i>functions return values in one of two static objects: abroken-down time structure and an array of type<b>char</b>.Execution of any of the functions may overwrite the informationreturned in either of these objects by any of the otherfunctions.<p>The<i>asctime()</i>interface need not be reentrant.<p>The<i>asctime_r()</i>function converts the broken-down timein the structure pointed to by<i>tm</i>into a string that is placed inthe user-supplied buffer pointed to by<i>buf</i>(which contains at least 26 bytes) and then returns<i>buf</i>.</blockquote><h4><a name = "tag_000_001_179"> </a>RETURN VALUE</h4><blockquote>Upon successful completion,<i>asctime()</i>returns a pointer to the string.<p>Upon successful completion,<i>asctime_r()</i>returns a pointer to a character string containing the date and time.This string is pointed to by the argument<i>buf</i>.If the function is unsuccessful,it returns NULL.</blockquote><h4><a name = "tag_000_001_180"> </a>ERRORS</h4><blockquote>No errors are defined.</blockquote><h4><a name = "tag_000_001_181"> </a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_000_001_182"> </a>APPLICATION USAGE</h4><blockquote>Values for the broken-down time structure can be obtained by calling<i><a href="gmtime.html">gmtime()</a></i>or<i><a href="localtime.html">localtime()</a></i>.This interface is included for compatibility with olderimplementations, and does not support localised date and timeformats.Applications should use<i><a href="strftime.html">strftime()</a></i>to achieve maximum portability.<br></blockquote><h4><a name = "tag_000_001_183"> </a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_000_001_184"> </a>SEE ALSO</h4><blockquote><i><a href="clock.html">clock()</a></i>,<i><a href="ctime.html">ctime()</a></i>,<i><a href="difftime.html">difftime()</a></i>,<i><a href="gmtime.html">gmtime()</a></i>,<i><a href="localtime.html">localtime()</a></i>,<i><a href="mktime.html">mktime()</a></i>,<i><a href="strftime.html">strftime()</a></i>,<i><a href="strptime.html">strptime()</a></i>,<i><a href="time.html">time()</a></i>,<i><a href="utime.html">utime()</a></i>,<i><a href="time.h.html"><time.h></a></i>.</blockquote><h4>DERIVATION</h4><blockquote><i>asctime()</i> derived from Issue 1 of the SVID.<p><i>asctime_r()</i> derived from the POSIX Threads Extension (1003.1c-1995).</blockquote><hr size=2 noshade><center><font size=2>UNIX ® is a registered Trademark of The Open Group.<br>Copyright © 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>⌨️ 快捷键说明
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