計算程式時間

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main()
{   
    clock_t t1, t2;
    t1 = clock();
    sleep(2);
    t2 = clock();
    printf("haha %lf\n", (t2-t1)/(double)(CLOCKS_PER_SEC));
    return 0;
}

我在virtualbox  , t1 , t2得到的都是0...



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

int main(int argc, char * argv[]){
    struct timeval test;           
    while(1){
        gettimeofday(&test, NULL);      //(2)
        printf("time %u:%u\n", test.tv_sec, test.tv_usec);
        sleep(2);
    }
    return 0;
}



#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(void)
{
    time_t t1,t2;
    t1=time(NULL);
    sleep(2);
    t2=time(NULL);
    printf("haha=%d\n",(int)difftime(t2,t1));
    return 0;
}



struct timeval {
time_t tv_sec; /* seconds */
suseconds_t tv_usec; /* microseconds */

};

struct timespec
{
    __time_t tv_sec;        /* Seconds. */
    long   tv_nsec;       /* Nanoseconds. */
};

#include <time.h>
int main(void){
    struct timespec start;
    if( clock_gettime( CLOCK_REALTIME, &start) == -1 ) {
  perror( "clock gettime" );
  exit( EXIT_FAILURE );
}
}


時間轉換
https://www.epochconverter.com/

gettimeofday() should never be used to measure time: 請用clock_gettime(), 不受ntpd更新時間後, 時間不準的問題
https://blog.habets.se/2010/09/gettimeofday-should-never-be-used-to-measure-time.html
https://blog.gtwang.org/programming/measure-the-execution-time-in-c-language/2/