Linux System Programming note 11 ——Time

Wall time(or real time)

Process time

Monotonic time

1. Breaking Down Time

struct tm{

     int tm_sec;

     int tm_min;

     int tm_hour;

     int tm_mday;

     int tm_mon;

     int tm_year;

     int tm_wday;

     int tm_yday;

     int tm_isdst;

#ifdef  _BSD_SOURCE

     long tm_gmtoff;

     const char *tm_zone;

#endif

};

2. POSIX Clocks

CLOCK_REALTIME

CLOCK_MONOTONIC

CLOCK_MONOTONIC_RAW

CLOCK_PROCESS_CPUTIME_ID

CLOCK_THREAD_CPUTIME_ID

3. Time Source Resolution

#include <time.h>

int clock_getres(clockid_t clock_id, struct timespec *res);

4. Getting the Current Time of Day

#include <time.h>

time_t time(time *t); //返回自epoch以来的秒数

5. A Better Interface

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

6. An Advanced Interface

#include <time.h>

int clock_gettime(clockid_t clock_id, struct timespec *ts);

7. Getting the Process Time

#include <sys/time.h>

struct tms {

     clock_t tms_utime;

     clock_t tms_stime;

     clock_t tms_cutime;

     clock_t tms_cstime;

};

clock_t times(struct tms *buf);

8. Setting the Current Time of Day

#define _SVID_SOURCE

#include <time.h>

int stime(time_t *t);

9. Setting Time with Precision

#include <sys/time.h>

int settimeofday(const struct timeval *tv,

                        const struct timezone *tz);

10. An Advanced Interface for Setting the Time

#include <time.h>

int clock_settime(clockid_t clock_id, const struct timespec *ts);

11. Playing with Time

#include <time.h>

char *asctime(const struct tm *tm); //不是线程安全的

char *asctime_r(const struct tm *tm, char *buf); // 线程安全的

#include <time.h>

time_t mktime(struct tm *tm);

#include <time.h>

char *ctime(const time_t *timep);

char *ctime_r(const time_t *timep, char *buf);

gmtime() converts the given time_t to a tm structure,

#include <time.h>

struct tm * gmtime(const time_t *timep);

struct tm *gmtime_r(const time_t *timep, struct tm *result);

#include <time.h>

struct tm *localtime(const time_t *timep);

struct tm *localtime_r(const time_t *timep, struct tm *result);

#include <time.h>

double difftime(time_t time1, time_t time2);

12. Timers

12.1 Simple Alarm

#include <unistd.h>

unsigned int alarm(unsigned int seconds);

12.2 Interval Timers

#include <sys/time.h>

int getitimer(int which, struct itimerval *value);

int setitimer(int which, struct itimerval *value, struct itimerval *ovaule);

struct itimerval {

     struct timeval it_interval;

     struct timeval it_value;

};

13. Advanced Timers

timer_create()

timer_settime()

timer_delete()