clock.3c (2010 09)

clock(3C) clock(3C)

NAME

clock( ) - report

CPU time used

SYNOPSIS

#include <time.h>

clock_t clock(void);

DESCRIPTION

clock() returns the amount of CPU time (in microseconds) used since the ﬁrst call to

clock(). The

time reported is the sum of the user and system times of the calling process and its terminated child

processes for which it has executed

wait()

, system() or pclose() (see wait (2) , system (3S), and

popen (3S)). To determine the time in seconds, the value returned by

clock() should be divided by the

value of the macro

CLOCKS_PER_SEC

The resolution of the clock varies, depending on the hardware and on software conﬁguration.

If the processor time used is not available or its value cannot be represented, the function returns the

value (

clock_t) − 1.

WARNINGS

The value returned by

clock() is deﬁned in microseconds for compatibility with systems that have

CPU

clocks with much higher resolution. Because of this, the value returned wraps around after accumulating

only 4295 seconds of CPU time (about 72 minutes).

DEPENDENCIES

The default clock resolution is 10 milliseconds.

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clock(3C) clock(3C) NAME clock( ) - report CPU time used SYNOPSIS #include clock_t clock(void); DESCRIPTION clock() returns the amount of CPU time (in microseconds) used since the first call to clock(). The time reported is the sum of the user and system times of the calling process and its terminated child processes for which it has executed wait() , system() or pclose() (see wait (2) , system (3S), and popen (3S)).
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(Notes) A (Notes) cA 2 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010