.TH CPUTIME 2
.SH NAME
cputime, times, cycles \- cpu time in this process and children
.SH SYNOPSIS
.B #include <u.h>
.br
.B #include <libc.h>
.PP
.ta \w'\fLdouble 'u
.B
long	times(long t[4])
.PP
.B
double	cputime(void)
.PP
.B
void	cycles(uvlong *cyclep)
.SH DESCRIPTION
If
.I t
is non-null,
.I times
fills it in
with the number of milliseconds spent in user code, system calls,
child processes in user code, and child processes in system calls.
.I Cputime
returns the sum of those same times, converted to seconds.
.I Times
returns the elapsed real time, in milliseconds, that the process has been running.
.PP
These functions read
.BR /dev/cputime ,
opening that file when they are first called.
.PP
.I Cycles
reads the processor's timestamp counter of cycles since reset,
if any, and stores it via
.IR cyclep .
Currently supported architectures are
.BR 386 ,
.BR amd64 ,
and
.BR power ;
on all others,
.I cycles
will store zero.
.SH SOURCE
.B /sys/src/libc/9sys
.br
.B /sys/src/libc/*/cycles.[cs]
.SH SEE ALSO
.IR exec (2),
.IR cons (3)
.SH BUGS
Only
.B 386
processors starting with the Pentium have timestamp counters;
calling
.I cycles
on earlier processors may execute an illegal instruction.