timespec

struct timespec {
    time_t tv_sec;  // 秒数
    long   tv_nsec; // 纳秒数
};

#include <stdio.h>
#include <time.h>

void some_function() {
    // 模拟一些工作
    for (volatile long i = 0; i < 1000000000; ++i);
}

int main() {
    struct timespec start, end;
    clock_gettime(CLOCK_MONOTONIC, &start); // 获取开始时间

    some_function(); // 执行代码

    clock_gettime(CLOCK_MONOTONIC, &end); // 获取结束时间

    // 计算时间差
    double elapsed_time = (end.tv_sec - start.tv_sec) + (end.tv_nsec - start.tv_nsec) / 1e9;
    printf("Elapsed time: %.9f seconds
", elapsed_time);

    return 0;
}

#include <stdio.h>
#include <time.h>
#include <errno.h>

int main() {
    struct timespec res;
    if (clock_getres(CLOCK_MONOTONIC, &res) == -1) {
        perror("clock_getres");
        return 1;
    }
    printf("Clock resolution: %ld.%09ld seconds
", res.tv_sec, res.tv_nsec);

    struct timespec start;
    if (clock_gettime(CLOCK_MONOTONIC, &start) == -1) {
        perror("clock_gettime");
        return 1;
    }
    printf("Current time: %ld.%09ld seconds since epoch
", start.tv_sec, start.tv_nsec);

    return 0;
}