1 .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
3 .\" %%%LICENSE_START(VERBATIM)
4 .\" Permission is granted to make and distribute verbatim copies of this
5 .\" manual provided the copyright notice and this permission notice are
6 .\" preserved on all copies.
8 .\" Permission is granted to copy and distribute modified versions of this
9 .\" manual under the conditions for verbatim copying, provided that the
10 .\" entire resulting derived work is distributed under the terms of a
11 .\" permission notice identical to this one.
13 .\" Since the Linux kernel and libraries are constantly changing, this
14 .\" manual page may be incorrect or out-of-date. The author(s) assume no
15 .\" responsibility for errors or omissions, or for damages resulting from
16 .\" the use of the information contained herein. The author(s) may not
17 .\" have taken the same level of care in the production of this manual,
18 .\" which is licensed free of charge, as they might when working
21 .\" Formatted or processed versions of this manual, if unaccompanied by
22 .\" the source, must acknowledge the copyright and authors of this work.
25 .\" Modified by Michael Haardt (michael@moria.de)
26 .\" Modified Sat Jul 24 14:29:17 1993 by Rik Faith (faith@cs.unc.edu)
27 .\" Modified 961203 and 001211 and 010326 by aeb@cwi.nl
28 .\" Modified 001213 by Michael Haardt (michael@moria.de)
29 .\" Modified 13 Jun 02, Michael Kerrisk <mtk.manpages@gmail.com>
30 .\" Added note on nonstandard behavior when SIGCHLD is ignored.
31 .\" Modified 2004-11-16, mtk, Noted that the nonconformance when
32 .\" SIGCHLD is being ignored is fixed in 2.6.9; other minor changes
33 .\" Modified 2004-12-08, mtk, in 2.6 times() return value changed
35 .\" Added notes on nonstandard behavior: Linux allows 'buf' to
36 .\" be NULL, but POSIX.1 doesn't specify this and it's nonportable.
38 .TH TIMES 2 2012-10-22 "Linux" "Linux Programmer's Manual"
40 times \- get process times
42 .B #include <sys/times.h>
44 .BI "clock_t times(struct tms *" buf );
47 stores the current process times in the
60 clock_t tms_utime; /* user time */
61 clock_t tms_stime; /* system time */
62 clock_t tms_cutime; /* user time of children */
63 clock_t tms_cstime; /* system time of children */
70 field contains the CPU time spent executing instructions
71 of the calling process.
74 field contains the CPU time spent in the system while
75 executing tasks on behalf of the calling process.
78 field contains the sum of the
82 values for all waited-for terminated children.
85 field contains the sum of the
89 values for all waited-for terminated children.
91 Times for terminated children (and their descendants)
92 are added in at the moment
96 returns their process ID.
97 In particular, times of grandchildren
98 that the children did not wait for are never seen.
100 All times reported are in clock ticks.
103 returns the number of clock ticks that have elapsed since
104 an arbitrary point in the past.
105 The return value may overflow the possible range of type
107 On error, \fI(clock_t)\ \-1\fP is returned, and
109 is set appropriately.
114 points outside the process's address space.
116 SVr4, 4.3BSD, POSIX.1-2001.
118 The number of clock ticks per second can be obtained using:
121 sysconf(_SC_CLK_TCK);
124 In POSIX.1-1996 the symbol \fBCLK_TCK\fP (defined in
126 is mentioned as obsolescent.
129 In Linux kernel versions before 2.6.9,
130 if the disposition of
134 then the times of terminated children
135 are automatically included in the
139 fields, although POSIX.1-2001 says that this should happen
140 only if the calling process
143 This nonconformance is rectified in Linux 2.6.9 and later.
144 .\" See the description of times() in XSH, which says:
145 .\" The times of a terminated child process are included... when wait()
146 .\" or waitpid() returns the process ID of this terminated child.
150 argument can be specified as NULL, with the result that
152 just returns a function result.
153 However, POSIX does not specify this behavior, and most
154 other UNIX implementations require a non-NULL value for
159 also returns a value of type
161 but this value is measured in units of
163 not the clock ticks used by
166 On Linux, the "arbitrary point in the past" from which the return value of
168 is measured has varied across kernel versions.
169 On Linux 2.4 and earlier this point is the moment the system was booted.
170 Since Linux 2.6, this point is \fI(2^32/HZ) \- 300\fP
171 (i.e., about 429 million) seconds before system boot time.
172 This variability across kernel versions (and across UNIX implementations),
173 combined with the fact that the returned value may overflow the range of
175 means that a portable application would be wise to avoid using this value.
176 To measure changes in elapsed time, use
177 .BR clock_gettime (2)
180 .\" On older systems the number of clock ticks per second is given
181 .\" by the variable HZ.
185 and the struct members are of type
187 although they store clock ticks, not seconds since the Epoch.
190 for the struct members, because it had no type
194 A limitation of the Linux system call conventions on some architectures
195 (notably i386) means that on Linux 2.6 there is a small time window
196 (41 seconds) soon after boot when
198 can return \-1, falsely indicating that an error occurred.
199 The same problem can occur when the return value wraps past
200 the maximum value that can be stored in
202 .\" The problem is that a syscall return of -4095 to -1
203 .\" is interpreted by glibc as an error, and the wrapper converts
204 .\" the return value to -1.
205 .\" http://marc.info/?l=linux-kernel&m=119447727031225&w=2
206 .\" "compat_sys_times() bogus until jiffies >= 0"
216 This page is part of release 3.79 of the Linux
219 A description of the project,
220 information about reporting bugs,
221 and the latest version of this page,
223 \%http://www.kernel.org/doc/man\-pages/.