To get a process' CPU time, you can use the clock function. This
facility is declared in the header file time.h.
In typical usage, you call the clock function at the beginning
and end of the interval you want to time, subtract the values, and then
divide by CLOCKS_PER_SEC (the number of clock ticks per second)
to get processor time, like this:
#include <time.h>
clock_t start, end;
double cpu_time_used;
start = clock();
... /* Do the work. */
end = clock();
cpu_time_used = ((double) (end - start)) / CLOCKS_PER_SEC;
Do not use a single CPU time as an amount of time; it doesn't work that
way. Either do a subtraction as shown above or query processor time
directly. See Processor Time.
Different computers and operating systems vary wildly in how they keep
track of CPU time. It's common for the internal processor clock
to have a resolution somewhere between a hundredth and millionth of a
second.
— Macro: int CLOCKS_PER_SEC
The value of this macro is the number of clock ticks per second measured
by the clock function. POSIX requires that this value be one
million independent of the actual resolution.
— Macro: int CLK_TCK
This is an obsolete name for CLOCKS_PER_SEC.
— Data Type: clock_t
This is the type of the value returned by the clock function.
Values of type clock_t are numbers of clock ticks.
— Function: clock_t clock (void)
This function returns the calling process' current CPU time. If the CPU
time is not available or cannot be represented, clock returns the
value (clock_t)(-1).
Published under the terms of the GNU General Public License
