C语言Time函数

1、 time() 获取当前时间

time_t timer;

time(&timer);

相当于 timer = time(NULL); 或 timer = time(0);

可用于随机数的生成。

srand( (unsigned)time(0));

2、localtime() 把一个时间戳转换 年月日表示格式

3、ctime() 把一个 时间戳转换为 年月日表示的字符串

char* ctime (const time_t * timer);

	struct tm * date;
	time_t now;
	time(&now);
	date = localtime(&now);

	//ctime() 演示
	char * datestr;
	datestr = ctime(&now);

	//mktime 演示
	time_t resTm = mktime(date);

	//strftime


	cout << now << endl;
	cout << date->tm_year << " " << date->tm_mon << " " << date->tm_mday << endl;
	cout << datestr << endl;
	cout << resTm << endl;

4 differtime 返回相隔的时（以秒为单位）

double difftime (time_t end, time_t beginning);

5 strftime()

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

把 timeptr 所指向的 时间格式化显示， 放在 pstr中。

specifier Replaced by Example

%a	Abbreviated weekday name *	Thu
%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	ShortMM/DD/YYdate, equivalent to%m/%d/%y	08/23/01
%e	Day of the month, space-padded (1-31)	23
%F	ShortYYYY-MM-DDdate, 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
%H	Hour in 24h format (00-23)	14
%I	Hour in 12h format (01-12)	02
%j	Day of the year (001-366)	235
%m	Month as a decimal number (01-12)	08
%M	Minute (00-59)	55
%n	New-line character ('\n')
%p	AM or PM designation	PM
%r	12-hour clock time *	02:55:02 pm
%R	24-hourHH:MMtime, equivalent to%H:%M	14:55
%S	Second (00-61)	02
%t	Horizontal-tab character ('\t')
%T	ISO 8601 time format (HH:MM:SS), equivalent to%H:%M:%S	14:55:02
%u	ISO 8601 weekday as number with Monday as1(1-7)	4
%U	Week number with the first Sunday as the first day of week one (00-53)	33
%V	ISO 8601 week number (00-53)	34
%w	Weekday as a decimal number with Sunday as0(0-6)	4
%W	Week number with the first Monday as the first day of week one (00-53)	34
%x	Date representation *	08/23/01
%X	Time representation *	14:55:02
%y	Year, last two digits (00-99)	01
%Y	Year	2001
%z	ISO 8601 offset from UTC in timezone (1 minute=1, 1 hour=100) If timezone cannot be termined, no characters	+100
%Z	Timezone name or abbreviation * If timezone cannot be termined, no characters	CDT
%%	A%sign	%

* The specifiers marked with an asterisk (*) are locale-dependent.
Note: Yellow rows indicate specifiers and sub-specifiers introduced by C99. Since C99, two locale-specific modifiers can also be inserted between the percentage sign ( % ) and the specifier proper to request an alternative format, where applicable:
Modifier Meaning Applies to

E	Uses the locale's alternative representation	%Ec %EC %Ex %EX %Ey %EY
O	Uses the locale's alternative numeric symbols	%Od %Oe %OH %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy