linux上的GetTickCount函数

#include <time.h>// 返回自系统开机以来的毫秒数（tick）unsigned long GetTickCount(){    struct timespec ts;    clock_gettime(CLOCK_MONOTONIC, &ts);    return (ts.tv_sec * 1000 + ts.tv_nsec / 1000000);}int main(){    struct timespec time1 = { 0, 0 };    clock_gettime(CLOCK_REALTIME, &time1);    printf("CLOCK_REALTIME: %d, %d\n", time1.tv_sec, time1.tv_nsec);    clock_gettime(CLOCK_MONOTONIC, &time1);    printf("CLOCK_MONOTONIC: %d, %d\n", time1.tv_sec, time1.tv_nsec);    clock_gettime(CLOCK_MONOTONIC_RAW, &time1);    printf("CLOCK_MONOTONIC_RAW: %d, %d\n", time1.tv_sec, time1.tv_nsec);    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time1);    printf("CLOCK_PROCESS_CPUTIME_ID: %d, %d\n", time1.tv_sec,           time1.tv_nsec);    clock_gettime(CLOCK_THREAD_CPUTIME_ID, &time1);    printf("CLOCK_THREAD_CPUTIME_ID: %d, %d\n", time1.tv_sec,           time1.tv_nsec);    printf("\n%d\n", time(NULL));    printf("tick count in ms: %ul\n", GetTickCount());    return 0;}