time.h詳細紹介

time.h詳細紹介

< ctime> (time.h)

                    。

一、Macro constants(マクロ定数)

CLOCKS_PER_SEC:ポタポタ音/秒、時間の単位

NULL:Nullポインタ

二、types(タイプ)

clock_t:クロックタイプ、クロックの滴下数を表す基本データタイプ

size_t:符号なし整数

time_t:時間タイプ、時間

を表す

struct tm:カレンダー、時間

を含む時間構造
Member
Type
Meaning
Range
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);
説明:特定の時間から消費される時間で、失敗した場合は-1を返します.

/* clock example: frequency of primes */
#include       /* printf */
#include        /* clock_t, clock, CLOCKS_PER_SEC */
#include        /* 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...
");
  f = frequency_of_primes (99999);
  printf ("The number of primes lower than 100,000 is: %d
",f);
  t = clock() - t;
  printf ("It took me %d clicks (%f seconds).
",t,((float)t)/CLOCKS_PER_SEC);
  return 0;
}

2、 double difftime (time_t end, time_t beginning);
説明:beginningからendまでの時間(end-beginning)(単位/秒)を計算します.

/* difftime example */
#include       /* 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.
", seconds);

  return 0;
}

3、 time_t mktime (struct tm * timeptr);
説明:

は、timeptrポインタ記述の時間を返し、時間が記述されていない場合は−1を返す.

localtimeの逆変換

構造メンバーtm_を無視wday and tm_yday;他のメンバーは有効範囲をタイムリーに超え、説明します.

/* mktime example: weekday calculator */
#include       /* 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.
", weekday[timeinfo->tm_wday]);

  return 0;
}

4、 time_t time (time_t* timer);
説明:

現在時刻を取得します.

時間ポインタがNULLでない場合、その指定された時間が返されます.

は時間を取得できず、-1に戻る.

が返す時間は、00:00 hours,Jan 1,1970 UTC

に基づいています.

/* time example */
#include       /* 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、変換
1、 char* asctime (const struct tm * timeptr);
説明:

  timeptr     ， C-     

     ：Www Mmm dd hh:mm:ss yyyy（            ）

      ，       

/* asctime example */
#include       /* printf */
#include        /* 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);
説明:

  timer     ， C-     

     ：Www Mmm dd hh:mm:ss yyyy（            ）

      ，       

 asctime(localtime(timer))  

/* ctime example */
#include       /* printf */
#include        /* 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);
説明:

  timer  tm   

 time_t     UTC time

/* gmtime example */
#include       /* puts, printf */
#include        /* 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
", (ptm->tm_hour+MST)%24, ptm->tm_min);
  printf ("Reykjavik (Iceland) : %2d:%02d
", (ptm->tm_hour+UTC)%24, ptm->tm_min);
  printf ("Beijing (China) :     %2d:%02d
", (ptm->tm_hour+CCT)%24, ptm->tm_min);

  return 0;
}

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

  timer  tm   

 time_t      local time

/* localtime example */
#include       /* puts, printf */
#include        /* 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 );
説明:

 timeptr    ，      ，   ptr 

 format  ，    timeptr ptr，  maxsize  。

ptr：    ，  C-   

maxsize：       ，   ptr      

format：  

   ：     ptr    （        ），     maxsize，  0

/* strftime example */
#include       /* puts */
#include        /* 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;
}

specifier
Replaced by
Example
%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