linux c++计算程序运行时长

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>

using namespace std;

int main()
{
    // 1. 
    // struct timeval start, end;
    // gettimeofday(&start, NULL);
    // system("pwd");
    // gettimeofday(&end, NULL);
    // int timeuse = 1000000 * (end.tv_sec - start.tv_sec) + end.tv_usec - start.tv_usec;
    // runTime  = timeStart.tv_sec + (double)(timeStart.tv_usec)/1000000；
    // printf("\nstart time: %d \nend time: %d \nspent time: %d us\n", &start, &end, timeuse);

    // 2. 
    struct timeval timeStart, timeEnd, timeSystemStart; 
    double runTime=0, systemRunTime; 
    gettimeofday(&timeStart, NULL );
    usleep(300000);
    gettimeofday( &timeEnd, NULL ); 
    runTime = (timeEnd.tv_sec - timeStart.tv_sec ) + (double)(timeEnd.tv_usec -timeStart.tv_usec)/1000000;  
    // systemRunTime = (timeEnd.tv_sec - timeSystemStart.tv_sec ) + (double)(timeEnd.tv_usec -timeSystemStart.tv_usec)/1000000;    
    printf("runTime is %lf s\n", runTime);         
    return 0;
}