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