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Diffstat (limited to 'man/man2/times.2')
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diff --git a/man/man2/times.2 b/man/man2/times.2 new file mode 100644 index 000000000..7e85beb6e --- /dev/null +++ b/man/man2/times.2 @@ -0,0 +1,222 @@ +.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992 +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.\" Modified by Michael Haardt (michael@moria.de) +.\" Modified Sat Jul 24 14:29:17 1993 by Rik Faith (faith@cs.unc.edu) +.\" Modified 961203 and 001211 and 010326 by aeb@cwi.nl +.\" Modified 001213 by Michael Haardt (michael@moria.de) +.\" Modified 13 Jun 02, Michael Kerrisk <mtk.manpages@gmail.com> +.\" Added note on nonstandard behavior when SIGCHLD is ignored. +.\" Modified 2004-11-16, mtk, Noted that the nonconformance when +.\" SIGCHLD is being ignored is fixed in Linux 2.6.9; other minor changes +.\" Modified 2004-12-08, mtk, in Linux 2.6 times() return value changed +.\" 2005-04-13, mtk +.\" Added notes on nonstandard behavior: Linux allows 'buf' to +.\" be NULL, but POSIX.1 doesn't specify this and it's nonportable. +.\" +.TH times 2 (date) "Linux man-pages (unreleased)" +.SH NAME +times \- get process times +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <sys/times.h> +.P +.BI "clock_t times(struct tms *" buf ); +.fi +.SH DESCRIPTION +.BR times () +stores the current process times in the +.I "struct tms" +that +.I buf +points to. +The +.I struct tms +is as defined in +.IR <sys/times.h> : +.P +.in +4n +.EX +struct tms { + clock_t tms_utime; /* user time */ + clock_t tms_stime; /* system time */ + clock_t tms_cutime; /* user time of children */ + clock_t tms_cstime; /* system time of children */ +}; +.EE +.in +.P +The +.I tms_utime +field contains the CPU time spent executing instructions +of the calling process. +The +.I tms_stime +field contains the CPU time spent executing inside the kernel +while performing tasks on behalf of the calling process. +.P +The +.I tms_cutime +field contains the sum of the +.I tms_utime +and +.I tms_cutime +values for all waited-for terminated children. +The +.I tms_cstime +field contains the sum of the +.I tms_stime +and +.I tms_cstime +values for all waited-for terminated children. +.P +Times for terminated children (and their descendants) +are added in at the moment +.BR wait (2) +or +.BR waitpid (2) +returns their process ID. +In particular, +times of grandchildren +that the children did not wait for are never seen. +.P +All times reported are in clock ticks. +.SH RETURN VALUE +.BR times () +returns the number of clock ticks that have elapsed since +an arbitrary point in the past. +The return value may overflow the possible range of type +.IR clock_t . +On error, +\fI(clock_t)\ \-1\fP is returned, +and +.I errno +is set to indicate the error. +.SH ERRORS +.TP +.B EFAULT +.I tms +points outside the process's address space. +.SH VERSIONS +On Linux, +the +.I buf +argument can be specified as NULL, +with the result that +.BR times () +just returns a function result. +However, +POSIX does not specify this behavior, +and most +other UNIX implementations require a non-NULL value for +.IR buf . +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +POSIX.1-2001, +SVr4, +4.3BSD. +.P +In POSIX.1-1996 the symbol \fBCLK_TCK\fP (defined in +.IR <time.h> ) +is mentioned as obsolescent. +It is obsolete now. +.P +Before Linux 2.6.9, +if the disposition of +.B SIGCHLD +is set to +.BR SIG_IGN , +then the times of terminated children +are automatically included in the +.I tms_cstime +and +.I tms_cutime +fields, +although POSIX.1-2001 says that this should happen +only if the calling process +.BR wait (2)s +on its children. +This nonconformance is rectified in Linux 2.6.9 and later. +.\" See the description of times() in XSH, which says: +.\" The times of a terminated child process are included... when wait() +.\" or waitpid() returns the process ID of this terminated child. +.P +On Linux, +the \[lq]arbitrary point in the past\[rq] +from which the return value of +.BR times () +is measured has varied across kernel versions. +On Linux 2.4 and earlier, +this point is the moment the system was booted. +Since Linux 2.6, +this point is \fI(2\[ha]32/HZ) \- 300\fP +seconds before system boot time. +This variability across kernel versions (and across UNIX implementations), +combined with the fact that the returned value may overflow the range of +.IR clock_t , +means that a portable application would be wise to avoid using this value. +To measure changes in elapsed time, +use +.BR clock_gettime (2) +instead. +.\" .P +.\" On older systems the number of clock ticks per second is given +.\" by the variable HZ. +.P +SVr1-3 returns +.I long +and the struct members are of type +.I time_t +although they store clock ticks, +not seconds since the Epoch. +V7 used +.I long +for the struct members, +because it had no type +.I time_t +yet. +.SH NOTES +The number of clock ticks per second can be obtained using: +.P +.in +4n +.EX +sysconf(_SC_CLK_TCK); +.EE +.in +.P +Note that +.BR clock (3) +also returns a value of type +.IR clock_t , +but this value is measured in units of +.BR CLOCKS_PER_SEC , +not the clock ticks used by +.BR times (). +.SH BUGS +A limitation of the Linux system call conventions on some architectures +(notably i386) means that on Linux 2.6 there is a small time window +(41 seconds) soon after boot when +.BR times () +can return \-1, +falsely indicating that an error occurred. +The same problem can occur when the return value wraps past +the maximum value that can be stored in +.BR clock_t . +.\" The problem is that a syscall return of -4095 to -1 +.\" is interpreted by glibc as an error, and the wrapper converts +.\" the return value to -1. +.\" http://marc.info/?l=linux-kernel&m=119447727031225&w=2 +.\" "compat_sys_times() bogus until jiffies >= 0" +.\" November 2007 +.SH SEE ALSO +.BR time (1), +.BR getrusage (2), +.BR wait (2), +.BR clock (3), +.BR sysconf (3), +.BR time (7) |