.\" Copyright (c) 1990, 1991, 1993
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.\" the American National Standards Committee X3, on Information
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.\"     @(#)clock.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: head/lib/libc/gen/clock.3 165903 2007-01-09 00:28:16Z imp $
.\"
.Dd June 4, 1993
.Dt CLOCK 3
.Os
.Sh NAME
.Nm clock
.Nd determine processor time used
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In time.h
.Ft clock_t
.Fn clock void
.Sh DESCRIPTION
The
.Fn clock
function
determines the amount of processor time used since the invocation of the
calling process, measured in
.Dv CLOCKS_PER_SEC Ns s
of a second.
.Sh RETURN VALUES
The
.Fn clock
function returns the amount of time used unless an error occurs, in which
case the return value is \-1.
.Sh SEE ALSO
.Xr getrusage 2 ,
.Xr clocks 7
.Sh STANDARDS
The
.Fn clock
function conforms to
.St -isoC .
However,
.St -susv2
requires
.Dv CLOCKS_PER_SEC
to be defined as one million.
.Fx
does not conform to this requirement;
changing the value would introduce binary incompatibility
and one million is still inadequate on modern processors.