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| author | Alejandro Colomar <alx.manpages@gmail.com> | 2022-09-05 23:03:38 +0200 |
|---|---|---|
| committer | Alejandro Colomar <alx.manpages@gmail.com> | 2022-09-05 23:03:47 +0200 |
| commit | 70ac1c4785fc1e158ab2349a962dba2526bf4fbc (patch) | |
| tree | bff270e2496dd284bccfc1271b43946f5d225224 /man/man3/clock.3 | |
| parent | 5423a6f86b2b920a5f3e8cf8d759b513050f2d33 (diff) | |
| download | man-pages-70ac1c4785fc1e158ab2349a962dba2526bf4fbc.tar.gz | |
src.mk, All pages: Move man* to man/
The root of the repository is becoming a bit overpopulated and
unorganized, due to the recent addition of more mandirs, and more
informative and configuration files too. Let's create a specific
mandir <man/> that contains the mandirs <man[1-8]*>.
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Diffstat (limited to 'man/man3/clock.3')
| -rw-r--r-- | man/man3/clock.3 | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/man/man3/clock.3 b/man/man3/clock.3 new file mode 100644 index 0000000000..9fa92fff56 --- /dev/null +++ b/man/man3/clock.3 @@ -0,0 +1,100 @@ +.\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de) +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.\" Modified Sat Jul 24 21:27:01 1993 by Rik Faith (faith@cs.unc.edu) +.\" Modified 14 Jun 2002, Michael Kerrisk <mtk.manpages@gmail.com> +.\" Added notes on differences from other UNIX systems with respect to +.\" waited-for children. +.TH CLOCK 3 2021-03-22 "Linux man-pages (unreleased)" +.SH NAME +clock \- determine processor time +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <time.h> +.PP +.B clock_t clock(void); +.fi +.SH DESCRIPTION +The +.BR clock () +function returns an approximation of processor time used by the program. +.SH RETURN VALUE +The value returned is the CPU time used so far as a +.IR clock_t ; +to get the number of seconds used, divide by +.BR CLOCKS_PER_SEC . +If the processor time used is not available or its value cannot +be represented, the function returns the value +.IR (clock_t)\ \-1 . +.SH ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.ad l +.nh +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.BR clock () +T} Thread safety MT-Safe +.TE +.hy +.ad +.sp 1 +.SH STANDARDS +POSIX.1-2001, POSIX.1-2008, C89, C99. +XSI requires that +.B CLOCKS_PER_SEC +equals 1000000 independent +of the actual resolution. +.SH NOTES +The C standard allows for arbitrary values at the start of the program; +subtract the value returned from a call to +.BR clock () +at the start of the program to get maximum portability. +.PP +Note that the time can wrap around. +On a 32-bit system where +.B CLOCKS_PER_SEC +equals 1000000 this function will return the same +value approximately every 72 minutes. +.PP +On several other implementations, +the value returned by +.BR clock () +also includes the times of any children whose status has been +collected via +.BR wait (2) +(or another wait-type call). +Linux does not include the times of waited-for children in the +value returned by +.BR clock (). +.\" I have seen this behavior on Irix 6.3, and the OSF/1, HP/UX, and +.\" Solaris manual pages say that clock() also does this on those systems. +.\" POSIX.1-2001 doesn't explicitly allow this, nor is there an +.\" explicit prohibition. -- MTK +The +.BR times (2) +function, which explicitly returns (separate) information about the +caller and its children, may be preferable. +.PP +In glibc 2.17 and earlier, +.BR clock () +was implemented on top of +.BR times (2). +For improved accuracy, +since glibc 2.18, it is implemented on top of +.BR clock_gettime (2) +(using the +.B CLOCK_PROCESS_CPUTIME_ID +clock). +.SH SEE ALSO +.BR clock_gettime (2), +.BR getrusage (2), +.BR times (2) |