NAME

     time -- get time of day

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <time.h>

     time_t

     time(time_t *tloc);

DESCRIPTION

     The time() function returns the value of time in seconds since  hours,  minutes,  seconds, January , , Coordinated Univer-

     sal Time, without including leap seconds.  If an error occurs, time() returns the value (time_t)-.

     The return value is also stored in *tloc, provided that tloc is non-null.

time函数说明

/**

 * Author: Yaowen Xu

 * Github: https://github.com/yaowenxu

 * Organization: 北航系统结构研究所

 * Date: 2019-08-18 13:03:53

 * LastEditTime: 2019-08-18 13:14:33

 * Description: 使用 C 语言库 time 函数 对程序运行计时 以秒为单位

 */

#include <time.h>

#include <stdio.h>

#include <math.h>

int str2int(char* str){

    char *p = str;

    int sum = ;

    while (*p != '\0')

    {

        sum = sum* + (*p-'');

        p++;

    }

    return sum;

}

int main(int argc, char* argv[]){

    time_t start, stop; // time_t aka long

    int def = ;

    if (argc == )

    {

        def = str2int(argv[argc-]);

    }

    start = time(NULL);

    for (int i = ; i < def ; i++)

    {

        float tmp = sqrt(i);

    }

    stop =  time(NULL);

    time_t total =  stop - start; // 使用运行的时间 以秒为单位

    printf("Start: %ld s\n", start);

    printf("Stop: %ld s\n", stop);

    printf("Time: %ld s\n", total); // 总共使用的时钟

    return ;

}