linux测耗时精确至微秒级

#include <stdio.h>
#include <string.h>
#include <sys/time.h>
#include <unistd.h>

int main(int argc, char **argv)
{
    struct timeval dwStart;
    struct timeval dwEnd;
    float dwTime = 0;

    gettimeofday(&dwStart, NULL);
    sleep(2);
    gettimeofday(&dwEnd, NULL);
    dwTime = 1000000 * (dwEnd.tv_sec - dwStart.tv_sec) + (dwEnd.tv_usec - dwStart.tv_usec);
    dwTime = dwTime / 1000000;
    printf("log --> %fs\n", dwTime);
    return 0;
}
--------------------------------------------------------------
output:
log --> 2.000512s