C Language Acquisition system time of several ways __c language

How to get time in C language . how accurate.
1 accurate to seconds using time_t time (time_t * timer)
2 using clock_t clock (), the CPU time is accurate to 1/clocks_per_sec seconds.
3 Calculating time difference using double difftime (time_t timer1, time_t Timer0)
4 Using the DWORD GetTickCount () to the millisecond
5 If you use MFC's CTime class, you can use Ctime::getcurrenttime () to get the exact second
6 to get high precision time, you can use
BOOL QueryPerformanceFrequency (Large_integer *lpfrequency)
Gets the frequency of the system's counters
BOOL QueryPerformanceCounter (Large_integer *lpperformancecount)
Get the value of a counter
Then use the difference of two times the counter divided by frequency to get the time.
7 Multimedia Timer functions
The following functions are used with multimedia timers.
Timebeginperiod/timeendperiod/timegetdevcaps/timegetsystemtime
//*********************************************************************
The function of obtaining the current system time with standard C implementation

A. Time () function

The

     time (&rawtime) function gets the number of seconds in the current time from January 1, 1970, in seconds Count units, in Rawtime.
#include "time.h"  
Void Main ()  
{ 
time_t rawtime; 
Struct TM * timeinfo; 
Time (&rawtime);  
Timeinfo = localtime (&rawtime);  
printf (/007the the current date/time is :%s, Asctime (Timeinfo));  
Exit (0);  
} 
================= 
#include  -- Required time function header file  
time_t--Time type (time.h definition is typedef long time_t;  traced, time_t is long)
struct TM--time structure, time.h definition As follows:  
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; 
Time (&rawti ME); --acquisition of time, in seconds, starting from January 1, 1970, in rawtime 
LocalTime (&rawtime);--to local time, TM time structure  
Asctime ()--to standard ASC II Time Format: &NBSP
Day of the week: minutes: Second year

-----------------------------------------------------------------------------
Two. Clock () function, using the clock () function, to get the system after the start of the millisecond time, and then divided by clocks_per_sec, can be replaced by "seconds", the standard C function.
clock_t clock (void);
#include
clock_t t = clock ();
Long sec = t/clocks_per_sec;
He is recording the clock cycle, the implementation does not appear to be very accurate, need to test validation;
---------------------------------------------------------------------------
Three. gettime (&t); It is said that the time structure of tc2.0 contains millisecond information
#include
#include
int main (void)
{
struct time t;
GetTime (&t);
printf ("The current time is:%2d:%02d:%02d.%0 2d/n ",
T.ti_hour, T.ti_min, T.ti_sec, T.ti_hund);
return 0;
}
Time is a struct in which the member function Ti_hund is milliseconds ...

--------------------------------------------------------------------------------
Four. GetTickCount (), this is a function commonly used in Windows to calculate the running time of the program;
DWORD Dwstart = GetTickCount ();
Here to run your program code
DWORD dwend = GetTickCount ();
Then (Dwend-dwstart) is your program run time, in milliseconds
This function is only accurate to 55ms,1 a tick is 55ms.
--------------------------------------------------------------------------------
Five. timeGetTime () T,imegettime () is basically equal to GetTickCount (), but the precision is higher
DWORD Dwstart = timeGetTime ();
Here to run your program code
DWORD dwend = timeGetTime ();
Then (Dwend-dwstart) is your program run time, in milliseconds
Although the returned value unit should be MS, the legendary precision is only 10ms.
=========================================
Unix
# #unix时间相关, it's a standard library.
//*********************************************************************
The 1.TIMEGM function simply converts the struct TM structure into a time_t structure and does not use time zone information;
time_t timegm (struct TM *tm);
2.mktime Use time zone information
time_t mktime (struct TM *tm);
The Timelocal function is the GNU extended equivalent to the POSIX function mktime
time_t timelocal (struct TM *tm);
The 3.gmtime function simply converts the time_t structure into a struct TM structure and does not use time zone information;
struct TM * gmtime (const time_t *clock);
4.localtime Use time zone information
struct TM * localtime (const time_t *clock);
1.time acquisition time, Stime set time
time_t T;
T = time (&t);
2.stime its parameter should be GMT time, set to local time according to local timezone;
int stime (time_t *tp)
3.utc=true indicates the use of daylight saving time;
4. File modification time and other information are all used GMT time storage, different systems in the modified time after the localtime conversion cost time;
5. Set time zone recommended to use setup;
6. Set time zone can also be accounts/etc/sysconfig/clock in the setting before ln-fs/usr/share/zoneinfo/xxxx/xxx/etc/localtime can be again effective
Time_t can only express the 68 range, that mktime can only return 1970-2038 of this range of time_t
See if your system has time_t64, it can indicate a larger time range
Windows
# #Window里面的一些不一样的
//*********************************************************************

I. CTime () class
VC programming typically uses the CTime class to get the current date and time

CTime t = getcurrenttime ();  
SYSTEMTIME structure contains millisecond information
typedef struct _SYSTEMTIME { 
WORD wyear; 
Word wmonth; 
Word wdayofweek; 
Word wday; 
Word whour; 
Word wminute; 
Word wsecond; 
Word wmilliseconds;
} SYSTEMTIME, *psystemtime;
SYSTEMTIME T1;
GetSystemTime (&t1)  
CTime curtime (t1);  
WORD ms = T1.WMILLISECONDS; 
SYSTEMTIME Systm;
:: Getlocaltime (&SYSTM);
_strtime ()//in time.h can only use
Char t[11] in Windows;
_strtime (t);
puts (t);

//*****************************
Get current date and time
CTime Tm=ctime::getcurrenttime ();
CString Str=tm. Format ("%y-%m-%d");
In VC, we can use CTime time class, get the system current date, the concrete usage method is as follows:
CTime t = ctime::getcurrenttime (); Get the system date, stored in t
int D=t.getday (); Get Current date
int Y=t.getyear (); Get Current year
int M=t.getmonth (); Get Current Month
int H=t.gethour (); Get the current for when
int Mm=t.getminute (); Get the current minute
int S=t.getsecond (); Get the current second
int W=t.getdayofweek (); Get day of the week, note 1 for Sunday, 7 for Saturday

Two. CTimeSpan class
If you want to calculate the difference between two periods of time, you can use the CTimeSpan class, using the following methods:
CTime T1 (1999, 3, 19, 22, 15, 0);
CTime t = ctime::getcurrenttime ();
CTimeSpan span=t-t1; Calculates the interval between the current system time and time T1
int Iday=span. GetDays (); How many days are there to get this time interval
int Ihour=span. Gettotalhours (); Get how many hours a total
int Imin=span. Gettotalminutes ()//Get the total number of minutes
int Isec=span. Gettotalseconds ()//Get total number of seconds

------------------------------------------------------------------------------

Three. _timeb () function
_timeb defined in Sys/timeb. H, there are four fields
Dstflag
Millitm
Time
TimeZone
void _ftime (struct _timeb *timeptr);
struct _TIMEB timebuffer;
_ftime (&timebuffer);
Take the current time: The document can be spoken to MS, someone tested, as if only to 16ms!

Four. Set Timer
Define Timer ID
#define Timerid_jisuanfangshi 2
Set the clock in place where it is needed to begin its function;
SetTimer (Timerid_jisuanfangshi,200,null);
Destroy the clock when the timer is not needed
KillTimer (Timerid_jisuanfangshi);
The message map of the corresponding VC program
void Cjisuan::ontimer (UINT nidevent)
{switch (nidevent)}
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# #如何设定当前系统时间---------------------------------------windows
SYSTEMTIME M_mylocaltime,*lpsystemtime;
m_mylocaltime.wyear=2003;
M_MYLOCALTIME.WM;
M_mylocaltime.wday=1;
m_mylocaltime.whour=0;
m_mylocaltime.wminute=0;
M_mylocaltime.wsec;
M_mylocaltime.wmillisec;
lpsystemtime=&m_mylocaltime;
if (Setlocaltime (lpsystemtime))//Here is replaced by SetSystemTime ()
MessageBox ("OK!");
Else
MessageBox ("Error!");
SYSTEMTIME M_mylocaltime,*lpsystemtime;
m_mylocaltime.wyear=2003;
M_MYLOCALTIME.WM;
M_mylocaltime.wday=1;
lpsystemtime=&m_mylocaltime;
if (setdate (lpsystemtime))//Here is replaced by SetSystemTime ()
MessageBox ("OK!");
Else
MessageBox ("Error!");

See the original: http://blog.163.com/gao_junfu/blog/static/91177329200962211185037/