在軟件設(shè)計(jì)中經(jīng)常會(huì)用到關(guān)于時(shí)間的處理，用來(lái)計(jì)算語(yǔ)句、函數(shù)的執(zhí)行時(shí)間，這時(shí)就需要精確到毫秒甚至是微妙的時(shí)間。

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int gettimeofday(struct timeval *tv, struct timezone *tz);

int settimeofday(const struct timeval *tv?, const struct timezone *tz);

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struct timeval {

??? time_t????? tv_sec;???? /* seconds */

??? suseconds_t tv_usec;??? /* microseconds */

};

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struct timezone {

??? int tz_minuteswest;???? /* minutes west of Greenwich */

??? int tz_dsttime;???????? /* type of DST correction */

};

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下面是個(gè)簡(jiǎn)單的例子，用來(lái)統(tǒng)計(jì)程序的執(zhí)行時(shí)間：

?????? …

struct timeval t_start,t_end;

??? long cost_time = 0;

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//get start time

gettimeofday(&t_start, NULL);

printf("Start time: %ld us", t_start.tv_usec);

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//some operation

…

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//get end time

gettimeofday(&t_end, NULL);

printf("End time: %ld us", t_end.tv_usec);

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//calculate time slot

cost_time = t_end.tv_usec - t_start.tv_usec;

printf("Cost time: %ld us", cost_time);

…

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輸出：

Start time: 438061 us

End time: 459867 us

Cost time: 21806 us

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demo:

#include <stdio.h> #include <stdlib.h> #include <sys/time.h> int main(int argc, char *argv[]) { printf("Hello, world!\n"); struct timeval tvafter,tvpre; struct timezone tz; int sum = 0; int i=0; gettimeofday (&tvpre , &tz);for(i = 0; i < 100000000; i++) {sum += i; } gettimeofday (&tvafter , &tz); printf("sum=%d 花費(fèi)時(shí)間:%d\n",sum, (tvafter.tv_sec-tvpre.tv_sec)*1000+(tvafter.tv_usec-tvpre.tv_usec)/1000); return EXIT_SUCCESS; }

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