Calculates the wall-clock time used by the calling process.
clock_t clock( void );
Return Value
The elapsed wall-clock time since the start of the process (elapsed time in seconds times CLOCKS_PER_SEC). If the amount of elapsed time is unavailable, the function returns –1, cast as a clock_t.
Remarks
The clock function tells how much time the calling process has used. A timer tick is approximately equal to 1/CLOCKS_PER_SEC second. In versions of Microsoft C before 6.0, the CLOCKS_PER_SEC constant was called CLK_TCK.
For additional compatibility information, see Compatibility in the Introduction.
Libraries
All versions of the C run-time libraries.
Example
// crt_clock.c
/* This example prompts for how long
* the program is to run and then continuously
* displays the elapsed time for that period.
*/
int main( void )
{
long i = 6000000L;
clock_t start, finish;
double duration;
/* Delay for a specified time. */
printf( "Delay for three seconds\n" );
sleep( (clock_t)3 * CLOCKS_PER_SEC );
printf( "Done!\n" );
/* Measure the duration of an event. */
printf( "Time to do %ld empty loops is ", i );
start = clock();
while( i-- )
;
finish = clock();
duration = (double)(finish - start) / CLOCKS_PER_SEC;
printf( "%2.1f seconds\n", duration );
}
/* Pauses for a specified number of milliseconds. */
void sleep( clock_t wait )
{
clock_t goal;
goal = wait + clock();
while( goal > clock() )
;
}
Sample Output
Delay for three seconds
Done!
Time to do 6000000 empty loops is 0.1 seconds