golang编程之时间编程
编程离不开时间,时间管理,严格的说分成两块,一个是当前的时刻,对应的是一个点,还有是一段时间间隔。本文简单的讲讲go的时间相关的编程,比较简单,高手可以一笑而过。
golang对时间的支持,是package time做的事儿,里面有好多的函数,我就不一一举例学习,毕竟这是官方文档干的事情。我们初步的学习下常用的函数。第一个是UNIX epoch time,确切的说就是自1970-01-01 00:00:00 GMT以来的秒数,不知道如何获取的,可以在shell下执行 date +%s
- manu@manu-hacks:~/code/go/self$ date
+%s
- 1385131172
- #include <time.h>
- time_t now = time(NULL);
- type Time
struct {
- // sec gives the number of seconds elapsed since
- // January 1, year 1 00:00:00 UTC.
- sec int64
-
- // nsec specifies a non-negative nanosecond
- // offset within the second named by Seconds.
- // It must be in the range
[0, 999999999].
- nsec int32
-
- // loc specifies the Location that should be used to
- // determine the minute, hour, month, day,
and year
- // that correspond to this Time.
- // Only the zero Time has a nil Location.
- // In that case it is interpreted to mean UTC.
- loc *Location
- }
- now
:= time.Now()
获取UNIX epoch time:
- var epoch_seconds int64 = now.Unix()
- func (t
Time) Year()
int
- cur_year := now.Year()
- func (t
Time) Month()
Month
- cur_month := now.Month()
- if cur_month == time.November {
- ...
- }
- const (
- January Month = 1
+ iota
- February
- March
- April
- May
- June
- July
- August
- September
- October
- November
- December
- )
- func (t Time) Date()
(year int, month Month, day
int)
- year,mon,day = now.Date()
-
- func (t Time) Hour() int
- cur_hour := now.Hour()
-
time还提供了Clock()的同时返回 hour,minute,second = now.Clock().
在C语言中,我们用gmtime_r获取UTC时间,localtime_r获取本地时间,Golang我们也可以做到
- #include<stdio.h>
- #include<stdlib.h>
- #include<time.h>
- int main()
- {
- time_t now
= time(NULL);
- printf("elapsed %d second since 1970-01-01 00:00:00\n",now);
- struct tm now_utc_tm ={0};
- if (gmtime_r(&now,&now_utc_tm)
!=
NULL)
- {
- printf("UTC time is %d-%02d-%02d %02d:%02d:%02d %s\n",
- now_utc_tm.tm_year+1900,now_utc_tm.tm_mon,
- now_utc_tm.tm_mday,now_utc_tm.tm_hour,
- now_utc_tm.tm_min,now_utc_tm.tm_sec,now_utc_tm.tm_zone);
- }
- struct tm now_local_tm =
{0} ;
- if(localtime_r(&now,&now_local_tm)
!=
NULL)
- {
- printf("local time is %d-%02d-%02d %02d:%02d:%02d %s\n",
- now_local_tm.tm_year+1900,now_local_tm.tm_mon,
- now_local_tm.tm_mday,now_local_tm.tm_hour,
- now_local_tm.tm_min, now_local_tm.tm_sec,now_local_tm.tm_zone);
- }
- return 0;
- }
- package main
- import "fmt"
- import "time"
- func main(){
-
- now :=
time.Now()
- year,mon,day
:=
now.UTC().Date()
- hour,min,sec
:=
now.UTC().Clock()
- zone,_ :=
now.UTC().Zone()
- fmt.Printf("UTC time is %d-%d-%d %02d:%02d:%02d %s\n",
- year,mon,day,hour,min,sec,zone)
- year,mon,day
= now.Date()
- hour,min,sec
= now.Clock()
- zone,_ =
now.Zone()
- fmt.Printf("local time is %d-%d-%d %02d:%02d:%02d %s\n",
- year,mon,day,hour,min,sec,zone)
- }
- C版本的输出
- ------------------
- UTC time is 2013-10-22 15:49:18 GMT
- local time is 2013-10-22 23:49:18 CST
- go版本的输出
- ---------------------
- UTC time is 2013-11-22 15:51:22 UTC
- local time is 2013-11-22 23:51:22 CST
我们另一个关心的话题,是时间间隔,比如我们profile一个以非常耗时的function,我们会在函数开始前记下时刻值,函数结束后,再次记录下时刻值,然后两者的差值,就是函数运行时间。
这表明Time是可以相减的,
- start_time :=
time.Now()
- expensive_function
- end_time :=time.Now()
- var duration Duration = end_time.Sub(start_time)
- type Duration int64
- const (
- Nanosecond Duration = 1
- Microsecond = 1000
* Nanosecond
- Millisecond = 1000
* Microsecond
- Second = 1000
* Millisecond
- Minute = 60
* Second
- Hour = 60
* Minute
- )
- now := time.Now()
- time.Sleep(3*time.Second);
- end_time := time.Now()
- var dur_time time.Duration
= end_time.Sub(now)
- var elapsed_min float64 = dur_time.Minutes()
- var elapsed_sec float64 = dur_time.Seconds()
- var elapsed_nano int64 = dur_time.Nanoseconds()
- fmt.Printf("elasped %f minutes or \nelapsed %f seconds or \nelapsed %d nanoseconds\n",
- elapsed_min,elapsed_sec,elapsed_nano)
- elasped 0.050005 minutes
or
- elapsed 3.000292 seconds
or
- elapsed 3000292435 nanoseconds
第二部分描述Duration明显用到了Sleep()函数,这个函数是以纳秒为单位的,相当于C语言中的nanosleep()
- #include <time.h>
- nanosleep(): _POSIX_C_SOURCE >= 199309L
- int nanosleep(const struct timespec *req, struct timespec *rem);
#include <unistd.h>
unsigned int sleep(unsigned int seconds);
如果sleep 3秒中需要写成:
- time.Sleep(3000000000)
- time.Sleep(3*time.Second);
这个time package还有很多其他的内容,我就不一一赘述了。
参考文献:
1 golang package time
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