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1 | .\" Hey Emacs! This file is -*- nroff -*- source. |
2 | .\" | |
3 | .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992 | |
4 | .\" | |
5 | .\" Permission is granted to make and distribute verbatim copies of this | |
6 | .\" manual provided the copyright notice and this permission notice are | |
7 | .\" preserved on all copies. | |
8 | .\" | |
9 | .\" Permission is granted to copy and distribute modified versions of this | |
10 | .\" manual under the conditions for verbatim copying, provided that the | |
11 | .\" entire resulting derived work is distributed under the terms of a | |
12 | .\" permission notice identical to this one. | |
13 | .\" | |
14 | .\" Since the Linux kernel and libraries are constantly changing, this | |
15 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
16 | .\" responsibility for errors or omissions, or for damages resulting from | |
17 | .\" the use of the information contained herein. The author(s) may not | |
18 | .\" have taken the same level of care in the production of this manual, | |
19 | .\" which is licensed free of charge, as they might when working | |
20 | .\" professionally. | |
21 | .\" | |
22 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
23 | .\" the source, must acknowledge the copyright and authors of this work. | |
24 | .\" | |
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) | |
305a0578 | 29 | .\" Modified 13 Jun 02, Michael Kerrisk <mtk-manpages@gmx.net> |
fea681da | 30 | .\" Added note on non-standard behaviour when SIGCHLD is ignored. |
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31 | .\" Modified 2004-11-16, mtk, Noted that the non-conformance when |
32 | .\" SIGCHLD is being ignored is fixed in 2.6.9; other minor changes | |
e263839c | 33 | .\" Modified 2004-12-08, mtk, in 2.6 times() return value changed |
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34 | .\" |
35 | .TH TIMES 2 2002-06-14 "Linux" "Linux Programmer's Manual" | |
36 | .SH NAME | |
37 | times \- get process times | |
38 | .SH SYNOPSIS | |
39 | .B #include <sys/times.h> | |
40 | .sp | |
41 | .BI "clock_t times(struct tms *" buf ); | |
42 | .SH DESCRIPTION | |
fea681da | 43 | .BR times () |
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44 | stores the current process times in the |
45 | .I "struct tms" | |
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46 | that |
47 | .IR buf | |
48 | points to. | |
49 | The | |
50 | .I struct tms | |
51 | is as defined in | |
52 | .IR <sys/times.h> : | |
53 | .sp | |
54 | .nf | |
55 | struct tms { | |
56 | .RS | |
57 | clock_t tms_utime; /* user time */ | |
58 | clock_t tms_stime; /* system time */ | |
59 | clock_t tms_cutime; /* user time of children */ | |
60 | clock_t tms_cstime; /* system time of children */ | |
61 | .RE | |
62 | }; | |
63 | .fi | |
64 | .LP | |
65 | The | |
66 | .I tms_utime | |
67 | field contains the CPU time spent executing instructions | |
68 | of the calling process. | |
69 | The | |
70 | .I tms_stime | |
71 | field contains the CPU time spent in the system while | |
72 | executing tasks on behalf of the calling process. | |
73 | The | |
74 | .I tms_cutime | |
75 | field contains the sum of the | |
76 | .I tms_utime | |
77 | and | |
78 | .I tms_cutime | |
79 | values for all waited-for terminated children. | |
80 | The | |
81 | .I tms_cstime | |
82 | field contains the sum of the | |
83 | .I tms_stime | |
84 | and | |
85 | .I tms_cstime | |
86 | values for all waited-for terminated children. | |
87 | .LP | |
88 | Times for terminated children (and their descendants) | |
89 | is added in at the moment | |
90 | .BR wait (2) | |
91 | or | |
92 | .BR waitpid (2) | |
93 | returns their process ID. In particular, times of grandchildren | |
94 | that the children did not wait for are never seen. | |
95 | .LP | |
96 | All times reported are in clock ticks. | |
97 | .SH "RETURN VALUE" | |
4c926acf | 98 | .BR times () |
fea681da | 99 | returns the number of clock ticks that have elapsed since |
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100 | an arbitrary point in the past. |
101 | For Linux 2.4 and earlier this point is the moment the system was booted. | |
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102 | Since Linux 2.6, this point is \fI(2^32/HZ) - 300\fP |
103 | (i.e., about 429 million) seconds before system boot time. | |
e263839c | 104 | The return value may overflow the possible range of type |
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105 | .I clock_t. |
106 | On error, \fI(clock_t) \-1\fP is returned, and | |
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107 | .I errno |
108 | is set appropriately. | |
109 | .SH NOTES | |
110 | The number of clock ticks per second can be obtained using | |
111 | .RS | |
112 | sysconf(_SC_CLK_TCK); | |
113 | .RE | |
114 | In POSIX-1996 the symbol CLK_TCK (defined in | |
115 | .IR <time.h> ) | |
116 | is mentioned as obsolescent. It is obsolete now. | |
117 | .PP | |
81841f39 | 118 | In Linux kernel versions before 2.6.9, |
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119 | if the disposition of |
120 | .B SIGCHLD | |
121 | is set to | |
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122 | .B SIG_IGN |
123 | then the times of terminated children | |
124 | are automatically included in the | |
125 | .I tms_cstime | |
126 | and | |
127 | .I tms_cutime | |
128 | fields, although POSIX 1003.1-2001 says that this should only happen | |
129 | if the calling process | |
130 | .BR wait ()s | |
131 | on its children. | |
81841f39 | 132 | This non-conformance is rectified in Linux 2.6.9 and later. |
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133 | .\" See the description of times() in XSH, which says: |
134 | .\" The times of a terminated child process are included... when wait() | |
135 | .\" or waitpid() returns the process ID of this termianted child. | |
136 | .LP | |
137 | Note that | |
138 | .BR clock (3) | |
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139 | returns values of type |
140 | .I clock_t | |
141 | that are not measured in clock ticks | |
142 | but in | |
143 | .BR CLOCKS_PER_SEC . | |
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144 | .SH "CONFORMING TO" |
145 | SVr4, SVID, POSIX, X/OPEN, BSD 4.3 | |
146 | .SH "HISTORICAL NOTES" | |
147 | SVr1-3 returns | |
4c926acf | 148 | .I long |
fea681da | 149 | and the struct members are of type |
4c926acf | 150 | .I time_t |
fea681da | 151 | although they store clock ticks, not seconds since the epoch. V7 used |
4c926acf | 152 | .I long |
fea681da | 153 | for the struct members, because it had no type |
4c926acf | 154 | .I time_t |
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155 | yet. |
156 | .PP | |
157 | On older systems the number of clock ticks per second is given | |
158 | by the variable HZ. | |
159 | .SH "SEE ALSO" | |
160 | .BR time (1), | |
161 | .BR getrusage (2), | |
162 | .BR wait (2), | |
163 | .BR clock (3), | |
164 | .BR sysconf (3) |