ctime 例子程序

ctime中提供两种数据：tm结构体和time_t

tm结构体里面显示存储年月日，小时，分钟，秒，毫秒。 sizeof(tm) == 36。

time_t是个int64_或者double类型。 sizeof(time_t) == 8

tm可以格式化为字符串。时间的比较，求和作差各种运算需要把tm转化为time_t，time_t 运算以秒为最小单位。

 

tm中tm_year是从1900开始，如果保存2011年，tm_year = 2011 - 1900。

tm_month 范围是0 - 11，所以正常月份需要减去1

 

mktime 函数将tm表示的本地时间转化为time_t， tm => time_t

localtime 函数将time_t表示的本地时间转化为tm结构体 time_t => tm

注意如果使用gmtime函数，结果会跟本地时间差8个小时，这个地理常识可以理解。

例子代码：

/* ctime example */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
void test1()
{
	tm start,end;
	start.tm_year = 2011-1900;		//年必须这么写
	start.tm_mon = 6;
	start.tm_mday = 20;
	start.tm_hour = 20;
	start.tm_min = 46;
	start.tm_sec = 45;
	//start.tm_isdst = 0;
	end.tm_year = 2011-1900;
	end.tm_mon = 6;
	end.tm_mday = 20;
	end.tm_hour = 20;
	end.tm_min = 45;
	end.tm_sec = 50;
	//end.tm_isdst = 0;
	double dif;
	//dif = difftime ( mktime(&end), mktime(&start) );
	time_t sta = mktime(&start);
	time_t ed = mktime(&end);
	dif = ed - sta;
	//dif = difftime ( mktime(&end), mktime(&start) );
	printf ("%.5lf minutes./n", dif / 60 );
	time_t new_end = ed + 3*60;		//3 minutes
	tm* new1 = localtime(&new_end);		//gmtime 是把time_t转化为国际标准时间
	// printf("sizeof tm = %d/n", sizeof(tm));		// 36
}
void test2()
{
	char timeStr[] = "2011-6-20 21:15:30";
	printf("source time string is: /t %s/n", timeStr);
	tm timeinfo;
	sscanf(timeStr, "%d-%d-%d %d:%d:%d", 
		&timeinfo.tm_year, &timeinfo.tm_mon, &timeinfo.tm_mday, 
		&timeinfo.tm_hour, &timeinfo.tm_min, &timeinfo.tm_sec);
	timeinfo.tm_year -= 1900;
	timeinfo.tm_mon -= 1;		//month: 0-11
	//////////////////////////////////////////////////////////////////////////
	//	transform tm to time_t
	//////////////////////////////////////////////////////////////////////////
	timeinfo.tm_year += 1900;
	timeinfo.tm_mon += 1;

	// tm => string
	char dest[100] = {0};
	sprintf(dest, "%d-%d-%d %d:%d:%d", 
		timeinfo.tm_year, timeinfo.tm_mon, timeinfo.tm_mday, 
		timeinfo.tm_hour, timeinfo.tm_min, timeinfo.tm_sec);
	printf("dest time string is: /t %s/n", dest);
	// string => tm
}
// source time string is:   2011-6-20 21:15:30
// dest time string is:     2011-6-20 21:15:30
//////////////////////////////////////////////////////////////////////////
//	"type = 2 server_channel = 6 time_section = [2011:06:01-14:40:30 2011:06:01-14:58:20]";
bool parseInitString(char* str, int& type, int& channel, char* timestr)
{
	char* token = "[] =";
	char* pch;
	type = -1;
	channel = -1;
	pch = strtok(str, token);				// type
	if ( 0!=strcmp(pch, "type") )
		return false;
	pch = strtok(NULL, token);			// 1
	type = atoi(pch);
	pch = strtok(NULL, token);			// server_channel
	if ( 0!=strcmp(pch, "server_channel") )
		return false;
	pch = strtok(NULL, token);			// 6
	channel = atoi(pch);
	pch = strtok(NULL, token);			// time_section
	if ( 0!=strcmp(pch, "time_section") )
		return false;
	pch = strtok(NULL, token);			// 2011:06:01-14:40:30
	strcat(timestr, pch);
	strcat(timestr, " ");
	pch = strtok(NULL, token);			// 2011:06:01-14:58:20
	strcat(timestr, pch);
	return true;
}
void tesr3()
{
	char str[] = "2011:06:01-14:40:30 2011:06:01-14:58:20";
	char str1[20] = {0};
	char str2[20] = {0};
	//sscanf(str, "%s %s", str1, str2);
	sscanf(str, "%[0-9,:-] %[0-9,:-]", str1, str2);
	int length = sizeof(str);
	puts(str1);
	puts(str2);
	int year;
	int month;
	int day;
	int hour;
	int minute;
	int second;
	sscanf(str1, "%d:%d:%d-%d:%d:%d", 
		&year, &month, &day, &hour, &minute, &second);
	printf("%d:%d:%d-%d:%d:%d/n", year, month, day, hour, minute, second);
	char initStr[] = "type = 2 server_channel = 6 time_section = [2011:06:01-14:40:30 2011:06:01-14:58:20]";
	char timestr[50] = {0};
	int type;
	int channel;
	if ( parseInitString(initStr, type, channel, timestr) )
	{
		printf("type = %d/n", type);
		printf("channel = %d/n", channel);
		printf("timesection = %s/n", timestr);
	}
}
int main ()
{
	//test1();
	//test2();
	//test3();
	time_t begtime = 1309502430;
	time_t end = begtime + 3*60;
	// localtime /	gmtime	 区别
	tm* tm_end = localtime(&end);
	//////////////////////////////////////////////////////////////////////////
	tm start;		//2011:06:01-14:40:30
	start.tm_year = 2011-1900;		//年必须这么写
	start.tm_mon = 6;
	start.tm_mday = 1;
	start.tm_hour = 14;
	start.tm_min = 40;
	start.tm_sec = 30;
	time_t beg1 = mktime(&start);			// 将tm转化为本地时间
	tm* start1 = localtime(&beg1);			//	将time_t转化为当地时间
	system("PAUSE");
	return 0;
}