---

layout: post title: "title" subtitle: "time" date: 2019-04-22 15:52:12 author: "soaringsoul" header-img: "img/posts/default_post.jpg" catalog: true tags: - tag

---

sleep

ifdef _WIN32

#include <windows.h>

void sleep(unsigned milliseconds)
{
    Sleep(milliseconds);
}

else

#include <unistd.h>

void sleep(unsigned milliseconds)
{
    usleep(milliseconds * 1000); // takes microseconds
}

endif

std::chrono::milliseconds timespan(111605); // or whatever
std::this_thread::sleep_for(timespan);

获取当前时间

#include <sys/time.h>
struct timeval {
    time_t      tv_sec;     /* seconds */
    suseconds_t tv_usec;    /* microseconds */
};

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

#include <time.h>
#include <sys/time.h>

struct timeval tv;
gettimeofday(&tv, NULL);
return tv.tv_sec * 1000 + tv.tv_usec / 1000;

time_t time(time_t *t); // 获取从UNIX元年开始计数的秒数

struct tm *gmtime_r(const time_t *timep, struct tm *result); //不会考虑机器所在时区，GMT时间
struct tm *localtime_r(const time_t *timep, struct tm *result); // 会考虑机器所在时区/etc/timezone, 由于需要处理时区，速度会比gmtime_r慢， 可以在调用gmtime_r前手动加上时区偏移秒数(eg 北京时间: 8*60*60)


struct tm {
    int tm_sec;    /* Seconds (0-60) */
    int tm_min;    /* Minutes (0-59) */
    int tm_hour;   /* Hours (0-23) */
    int tm_mday;   /* Day of the month (1-31) */
    int tm_mon;    /* Month (0-11) */
    int tm_year;   /* Year - 1900 */
    int tm_wday;   /* Day of the week (0-6, Sunday = 0) */
    int tm_yday;   /* Day in the year (0-365, 1 Jan = 0) */
    int tm_isdst;  /* Daylight saving time */
};

time_t *timep 为日历时间(calendar time), 日历时间指距离1970-01-01 00:00:00 +0000 (UTC)的秒数

    time_t local_time = time(NULL);
    struct tm stime;   //tm结构指针
    localtime_r(&local_time, &stime);   //获取当地日期和时间

    // 线程不安全
    #include <time.h>
    time_t local_time = time(NULL);
    struct tm* stime = localtime(&local_time);

std::localtime (非线程安全)

std::localtime is not thread-safe because it uses a static buffer (shared between threads)

localtime_r （线程安全)

时间格式化

size_t strftime(char *s, size_t max, const char *format, const struct tm *tm);
char *strptime(const char *s, const char *format, struct tm *tm);