freebsd-dev/lib/libc/gen/clock.3
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.\" Copyright (c) 1990, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
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.\" @(#)clock.3 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.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.