clock - Determine processor time
The clock() function returns an approximation of processor
time used by the program.
The value returned is the CPU time used so far as a
clock_t; to get the number of seconds used, divide by
ANSI C. POSIX requires that CLOCKS_PER_SEC equals 1000000
independent of the actual resolution.
The C standard allows for arbitrary values at the start of
the program; take the difference between the value
returned from a call to clock() at the start of the pro
gram and the end to get maximum portability.
Note that the time can wrap around. On a 32bit system
where CLOCKS_PER_SEC equals 1000000 this function will
return the same value approximately every 72 minutes.
The times() function call returns more information.