time.h 詳細介紹

< ctime> (time.h)包含獲得和使用日期和時間信息的函數的定義。

一、Macro constants（宏常量）

• CLOCKS_PER_SEC：滴答聲/秒，時間的單位
• NULL：空指針

二、types（類型）

• clock_t：時鐘類型，表示時鐘滴答數的基本數據類型

• size_t：無符號整型

• time_t：時間類型，表示時間

• struct tm：時間結構，包含日歷、時間

MemberTypeMeaningRange

tm_sec	int	seconds	after the minute0-60*
tm_min	int	minutes	after the hour 0-59
tm_hour	int	hours	since midnight 0-23
tm_mday	int	day	of the month 1-31
tm_mon	int	months	since January 0-11
tm_year	int	years	since 1900
tm_wday	int	days	since Sunday 0-6
tm_yday	int	days	since January 1 0-365
tm_isdst	int	Daylight	Saving Time flag

三、時間操作

1、clock_t clock (void);

描述：從特定時間開始消耗的時間，如果失敗，返回-1。

/* clock example: frequency of primes */ #include <stdio.h> /* printf */ #include <time.h> /* clock_t, clock, CLOCKS_PER_SEC */ #include <math.h> /* sqrt */int frequency_of_primes (int n) {int i,j;int freq=n-1;for (i=2; i<=n; ++i) for (j=sqrt(i);j>1;--j) if (i%j==0) {--freq; break;}return freq; }int main () {clock_t t;int f;t = clock();printf ("Calculating...\n");f = frequency_of_primes (99999);printf ("The number of primes lower than 100,000 is: %d\n",f);t = clock() - t;printf ("It took me %d clicks (%f seconds).\n",t,((float)t)/CLOCKS_PER_SEC);return 0; }

2、double difftime (time_t end, time_t beginning);

描述：計算從beginning到end的時間(end-beginning)（單位/秒）。

/* difftime example */ #include <stdio.h> /* printf */ #include <time.h> /* time_t, struct tm, difftime, time, mktime */int main () {time_t now;struct tm newyear;double seconds;time(&now); /* get current time; same as: now = time(NULL) */newyear = *localtime(&now);newyear.tm_hour = 0; newyear.tm_min = 0; newyear.tm_sec = 0;newyear.tm_mon = 0; newyear.tm_mday = 1;seconds = difftime(now,mktime(&newyear));printf ("%.f seconds since new year in the current timezone.\n", seconds);return 0; }

3、time_t mktime (struct tm * timeptr);

描述：

• 返回timeptr指針描述的時間，如果時間未描述，返回-1。

• localtime的逆變換

• 忽略結構成員tm_wday and tm_yday；其他成員及時超出有效范圍，也將解釋。

/* mktime example: weekday calculator */ #include <stdio.h> /* printf, scanf */ #include <time.h> /* time_t, struct tm, time, mktime */int main () {time_t rawtime;struct tm * timeinfo;int year, month ,day;const char * weekday[] = { "Sunday", "Monday","Tuesday", "Wednesday","Thursday", "Friday", "Saturday"};/* prompt user for date */printf ("Enter year: "); fflush(stdout); scanf ("%d",&year);printf ("Enter month: "); fflush(stdout); scanf ("%d",&month);printf ("Enter day: "); fflush(stdout); scanf ("%d",&day);/* get current timeinfo and modify it to the user's choice */time ( &rawtime );timeinfo = localtime ( &rawtime );timeinfo->tm_year = year - 1900;timeinfo->tm_mon = month - 1;timeinfo->tm_mday = day;/* call mktime: timeinfo->tm_wday will be set */mktime ( timeinfo );printf ("That day is a %s.\n", weekday[timeinfo->tm_wday]);return 0; }

4、time_t time (time_t* timer);

描述：

• 獲取當前時間。

• 如果時間指針不為NULL，將返回其指向的時間。

• 不能取得時間，返回-1.

• 返回的時間基于： 00:00 hours, Jan 1, 1970 UTC

/* time example */ #include <stdio.h> /* printf */ #include <time.h> /* time_t, struct tm, difftime, time, mktime */int main () {time_t timer;struct tm y2k = {0};double seconds;y2k.tm_hour = 0; y2k.tm_min = 0; y2k.tm_sec = 0;y2k.tm_year = 100; y2k.tm_mon = 0; y2k.tm_mday = 1;time(&timer); /* get current time; same as: timer = time(NULL) */seconds = difftime(timer,mktime(&y2k));printf ("%.f seconds since January 1, 2000 in the current timezone", seconds);return 0; }

四、轉換

1、char* asctime (const struct tm * timeptr);

描述：

返回timeptr指針的時間，用C-字符串描述返回類型為：Www Mmm dd hh:mm:ss yyyy（星期 月 日 時分秒 年）輸出在新一行，以空字符串結束 /* asctime example */ #include <stdio.h> /* printf */ #include <time.h> /* time_t, struct tm, time, localtime, asctime */int main () {time_t rawtime;struct tm * timeinfo;time ( &rawtime );timeinfo = localtime ( &rawtime );printf ( "The current date/time is: %s", asctime (timeinfo) );return 0; }

2、char* ctime (const time_t * timer);

描述：

返回timer指針的時間，用C-字符串描述返回類型為：Www Mmm dd hh:mm:ss yyyy（星期 月 日 時分秒 年）輸出在新一行，以空字符串結束和asctime(localtime(timer))一樣 /* ctime example */ #include <stdio.h> /* printf */ #include <time.h> /* time_t, time, ctime */int main () {time_t rawtime;time (&rawtime);printf ("The current local time is: %s", ctime (&rawtime));return 0; }

3、struct tm * gmtime (const time_t * timer);

描述：

利用timer填充tm結構體把time_t時間轉化為UTC time /* gmtime example */ #include <stdio.h> /* puts, printf */ #include <time.h> /* time_t, struct tm, time, gmtime */#define MST (-7) #define UTC (0) #define CCT (+8)int main () {time_t rawtime;struct tm * ptm;time ( &rawtime );ptm = gmtime ( &rawtime );puts ("Current time around the World:");printf ("Phoenix, AZ (U.S.) : %2d:%02d\n", (ptm->tm_hour+MST)%24, ptm->tm_min);printf ("Reykjavik (Iceland) : %2d:%02d\n", (ptm->tm_hour+UTC)%24, ptm->tm_min);printf ("Beijing (China) : %2d:%02d\n", (ptm->tm_hour+CCT)%24, ptm->tm_min);return 0; }

4、struct tm * localtime (const time_t * timer);

描述：

利用timer填充tm結構體把time_t時間轉化為 local time /* localtime example */ #include <stdio.h> /* puts, printf */ #include <time.h> /* time_t, struct tm, time, localtime */int main () {time_t rawtime;struct tm * timeinfo;time (&rawtime);timeinfo = localtime (&rawtime);printf ("Current local time and date: %s", asctime(timeinfo));return 0; }

5、·size_t strftime (char* ptr, size_t maxsize, const char* format,const struct tm* timeptr );

描述：

把timeptr中的時間，以特定的格式，復制到ptr中以format格式，復制時間timeptr到ptr，最多maxsize字符。ptr：目的數組，存儲C-字符串maxsize：包括末尾空字符，復制到ptr的最大字符數format：格式返回值：返回復制到ptr的字符數（不包括末尾空字符），若超出范圍maxsize，返回0 /* strftime example */ #include <stdio.h> /* puts */ #include <time.h> /* time_t, struct tm, time, localtime, strftime */int main () {time_t rawtime;struct tm * timeinfo;char buffer [80];time (&rawtime);timeinfo = localtime (&rawtime);strftime (buffer,80,"Now it's %I:%M%p.",timeinfo);puts (buffer);return 0; } specifierReplaced byExample

%a	Abbreviated	weekday name *
%A	Full weekday name *	Thursday
%b	Abbreviated month name *	Aug
%B	Full month name *	August
%c	Date and time representation *	Thu Aug 23 14:55:02 2001
%C	Year divided by 100 and truncated to integer (00-99)	20
%d	Day of the month, zero-padded (01-31)	23
%D	Short MM/DD/YY date, equivalent to %m/%d/%y	08/23/01
%e	Day of the month, space-padded ( 1-31)	23
%F	Short YYYY-MM-DD date, equivalent to %Y-%m-%d	2001-08-23
%g	Week-based year, last two digits (00-99)	01
%G	Week-based year	2001
%h	Abbreviated month name * (same as %b)	Aug

總結

以上是生活随笔為你收集整理的time.h 详细介绍的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。