2010.12.22-time.h包含的库函数 一些常用的时间函数

这几个是我一个个试出来的，很好用的。呵呵，希望对你有用！

/*clock计算调用进程使用处理器的时间
函数原型：clock_t clock(void)*/
//实例
//******C语言描述******
#include
#include
#include

void sleep(clock_t wait);

int main(void)
{
    long i=6000000L;
    clock_t start,finish;
    double duration;
    printf("Delay for three seconds/n");
    sleep((clock_t)3*CLOCKS_PER_SEC);
    printf("Done!/n");
    printf("Time to do %ld empty loops is",i);
    start=clock();
    while(i--);
    finish=clock();
    duration=(double)(finish-start)/CLOCKS_PER_SEC;
    printf("%2.lf seconds/n",duration);
}

void sleep(clock_t wait)
{
    clock_t goal;
    goal=wait+clock();
    while(goal>clock());
}
//******C++语言描述******
#include
#include
#include
#include
using namespace std;

void sleep(clock_t wait);

int main(void)
{
    long i=6000000L;
    clock_t start,finish;
    double duration;
    cout<<"Delay for three seconds/n";
    sleep((clock_t)3*CLOCKS_PER_SEC);
    cout<<"Done!/n";
    cout<<"Time to do "<     start=clock();
    while(i--);
    finish=clock();
    duration=(double)(finish-start)/CLOCKS_PER_SEC;
    cout< }

void sleep(clock_t wait)
{
    clock_t goal;
    goal=wait+clock();
    while(goal>clock());
}

//******运行结果******
Delay for three seconds
Done!
Time to do 6000000 empty loops is 0.02 seconds
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//difftime计算t1,t2两个时间差
//函数原型：double difftime(time_t t1,time_t t2);t1开始时间 ,t2结束时间
//实例：
#include
#include
#include
#include
using namespace std;

int main(void)
{
    time_t start,finish;
    long loop;
    double result,elapsed_time;
    cout<<"Multiplying 2 floating point number 500 million times ..../n";
    time(&start);
    for(loop=0;loop<500000000;loop++)
        result=3.63*5.27;
    time(&finish);
    elapsed_time=difftime(finish,start);
    cout<<"Program takes "<     return 0;
}
//******运行结果******
Multiplying 2 floating point number 500 million times ....
Program takes 2 seconds.
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//asctime把时间日期转换为字符串
//函数原型：char *asctime(const struct tm *timeptr);timeptr时间日期结构指针
//实例：
//#include
#include
#include
//using namespace std;

struct tm *newtime;
time_t aclock;
int main(void)
{
    time(&aclock);
    newtime=localtime(&aclock);
    printf("current data and time %s",asctime(newtime));
    //return 0;
}
//******运行结果******
current data and time Sun Jul 01 17:23:49 2007
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