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diff --git a/man3/clock.3 b/man3/clock.3 new file mode 100644 index 000000000..676f4807d --- /dev/null +++ b/man3/clock.3 @@ -0,0 +1,81 @@ +.\" (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de) +.\" +.\" Permission is granted to make and distribute verbatim copies of this +.\" manual provided the copyright notice and this permission notice are +.\" preserved on all copies. +.\" +.\" Permission is granted to copy and distribute modified versions of this +.\" manual under the conditions for verbatim copying, provided that the +.\" entire resulting derived work is distributed under the terms of a +.\" permission notice identical to this one. +.\" +.\" Since the Linux kernel and libraries are constantly changing, this +.\" manual page may be incorrect or out-of-date. The author(s) assume no +.\" responsibility for errors or omissions, or for damages resulting from +.\" the use of the information contained herein. The author(s) may not +.\" have taken the same level of care in the production of this manual, +.\" which is licensed free of charge, as they might when working +.\" professionally. +.\" +.\" Formatted or processed versions of this manual, if unaccompanied by +.\" the source, must acknowledge the copyright and authors of this work. +.\" License. +.\" Modified Sat Jul 24 21:27:01 1993 by Rik Faith (faith@cs.unc.edu) +.\" Modified 14 Jun 2002, Michael Kerrisk <mtk16@ext.canterbury.ac.nz> +.\" Added notes on differences from other Unices with respect to +.\" waited-for children. +.TH CLOCK 3 2002-06-14 "GNU" "Linux Programmer's Manual" +.SH NAME +clock \- Determine processor time +.SH SYNOPSIS +.nf +.B #include <time.h> +.sp +.B clock_t clock(void); +.fi +.SH DESCRIPTION +The +.B 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 +.BR 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 (clock_t)-1. +.SH "CONFORMING TO" +ANSI C. +POSIX requires that 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 +.B clock() +at the start of the program to get maximum portability. +.PP +Note that the time can wrap around. On a 32bit system where +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 () +(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 behaviour on Irix 6.3, and the OSF/1, HP/UX, and +.\" Solaris manual pages say that clock() also does this on those systems. +.\" POSIX 1003.1-2001 doesn't explicitly allow this, nor is there an +.\" explicit prohibition. -- MTK +The +.B times() +function, which explicitly returns (separate) information about the +caller and its children, may be preferable. +.SH "SEE ALSO" +.BR getrusage (2), +.BR times (2) |