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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>times</title></head><body bgcolor="white"><basefont size="3"> <a name="times"></a> <a name="tag_03_779"></a><!-- times --> <!--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_779_01"></a>NAME</h4><blockquote>times - get process and waited-for child process times</blockquote><h4><a name="tag_03_779_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/sys/times.h.html">sys/times.h</a>><br><br> clock_t times(struct tms *</tt><i>buffer</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_779_03"></a>DESCRIPTION</h4><blockquote><p>The <i>times</i>() function shall fill the <b>tms</b> structure pointed to by <i>buffer</i> with time-accounting information.The <b>tms</b> structure is defined in <a href="../basedefs/sys/times.h.html"><i><sys/times.h></i></a>.</p><p>All times are measured in terms of the number of clock ticks used.</p><p>The times of a terminated child process shall be included in the <i>tms_cutime</i> and <i>tms_cstime</i> elements of the parentwhen <a href="../functions/wait.html"><i>wait</i>()</a> or <a href="../functions/waitpid.html"><i>waitpid</i>()</a> returns theprocess ID of this terminated child. If a child process has not waited for its children, their times shall not be included in itstimes.</p><ul><li><p>The <i>tms_utime</i> structure member is the CPU time charged for the execution of user instructions of the calling process.</p></li><li><p>The <i>tms_stime</i> structure member is the CPU time charged for execution by the system on behalf of the calling process.</p></li><li><p>The <i>tms_cutime</i> structure member is the sum of the <i>tms_utime</i> and <i>tms_cutime</i> times of the childprocesses.</p></li><li><p>The <i>tms_cstime</i> structure member is the sum of the <i>tms_stime</i> and <i>tms_cstime</i> times of the childprocesses.</p></li></ul></blockquote><h4><a name="tag_03_779_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>times</i>() shall return the elapsed real time, in clock ticks, since an arbitrary point in thepast (for example, system start-up time). This point does not change from one invocation of <i>times</i>() within the process toanother. The return value may overflow the possible range of type <b>clock_t</b>. If <i>times</i>() fails, (<b>clock_t</b>)-1 shallbe returned and <i>errno</i> set to indicate the error.</p></blockquote><h4><a name="tag_03_779_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_779_06"></a>EXAMPLES</h4><blockquote><h5><a name="tag_03_779_06_01"></a>Timing a Database Lookup</h5><p>The following example defines two functions, <i>start_clock</i>() and <i>end_clock</i>(), that are used to time a lookup. Italso defines variables of type <b>clock_t</b> and <b>tms</b> to measure the duration of transactions. The <i>start_clock</i>()function saves the beginning times given by the <i>times</i>() function. The <i>end_clock</i>() function gets the ending times andprints the difference between the two times.</p><pre><tt>#include <sys/times.h>#include <stdio.h>...void start_clock(void);void end_clock(char *msg);...static clock_t st_time;static clock_t en_time;static struct tms st_cpu;static struct tms en_cpu;...voidstart_clock(){ st_time = times(&st_cpu);}<br>/* This example assumes that the result of each subtraction is within the range of values that can be represented in an integer type. */voidend_clock(char *msg){ en_time = times(&en_cpu);<br> fputs(msg,stdout); printf("Real Time: %jd, User Time %jd, System Time %jd\n", (intmax_t)(en_time - st_time), (intmax_t)(en_cpu.tms_utime - st_cpu.tms_utime), (intmax_t)(en_cpu.tms_stime - st_cpu.tms_stime));}</tt></pre></blockquote><h4><a name="tag_03_779_07"></a>APPLICATION USAGE</h4><blockquote><p>Applications should use <i>sysconf</i>(_SC_CLK_TCK) to determine the number of clock ticks per second as it may vary from systemto system.</p></blockquote><h4><a name="tag_03_779_08"></a>RATIONALE</h4><blockquote><p>The accuracy of the times reported is intentionally left unspecified to allow implementations flexibility in design, fromuniprocessor to multi-processor networks.</p><p>The inclusion of times of child processes is recursive, so that a parent process may collect the total times of all of itsdescendants. But the times of a child are only added to those of its parent when its parent successfully waits on the child. Thus,it is not guaranteed that a parent process can always see the total times of all its descendants; see also the discussion of theterm ``realtime'' in <a href="alarm.html"><i>alarm</i>()</a>.</p><p>If the type <b>clock_t</b> is defined to be a signed 32-bit integer, it overflows in somewhat more than a year if there are 60clock ticks per second, or less than a year if there are 100. There are individual systems that run continuously for longer thanthat. This volume of IEEE Std 1003.1-2001 permits an implementation to make the reference point for the returned value bethe start-up time of the process, rather than system start-up time.</p><p>The term ``charge'' in this context has nothing to do with billing for services. The operating system accounts for time used inthis way. That information must be correct, regardless of how that information is used.</p></blockquote><h4><a name="tag_03_779_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_779_10"></a>SEE ALSO</h4><blockquote><p><a href="alarm.html"><i>alarm</i>()</a>, <a href="exec.html"><i><a href="../functions/exec.html">exec</a></i>()</a>, <a href="fork.html"><i>fork</i>()</a>, <a href="sysconf.html"><i>sysconf</i>()</a>, <a href="time.html"><i>time</i>()</a>, <a href="wait.html"><i>wait</i>()</a>, the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/sys/times.h.html"><i><sys/times.h></i></a></p></blockquote><h4><a name="tag_03_779_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from Issue 1 of the SVID.</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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