t时钟函数c语言,c语言clock函数使用示例

clock_t clock( void );

Calculates the processor time used by the calling process

head file is

Return Value

clock returns the number of clock ticks of elapsed processor time. The returned value

is the product of the amount of time that has elapsed since the start of a process and

the value of the CLOCKS_PER_SEC constant. If the amount of elapsed time is

unavailable, the function returns –1, cast as a clock_t.

Remarks

The clock function tells how much processor time the calling process has used. The

time in seconds is approximated by dividing the clock return value by the value of the

CLOCKS_PER_SEC constant. In other words, clock returns the number of

processor timer ticks that have elapsed. 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.

代码如下:

/* CLOCK.C: This example prompts for how long

* the program is to run and then continuously

* displays the elapsed time for that period.

*/

#include

#include

#include

void sleep( clock_t wait );

void main( void )

{

long    i = 600000000L;

clock_t start, finish;

double  duration;

/* Delay for a specified time. */

printf( "Delay for three secondsn" );

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 secondsn", duration );

}

/* Pauses for a specified number of milliseconds. */

void sleep( clock_t wait )

{

clock_t goal;

goal = wait + clock();

while( goal > clock() )

}//sleep