time, _time32, _time64

项目
12/18/2017

The latest version of this topic can be found at time, _time32, _time64.

Get the system time.

Syntax

time_t time(  
   time_t *timer   
);  
__time32_t _time32(  
   __time32_t *timer   
);  
__time64_t _time64(  
   __time64_t *timer   
);

Parameters

timer
Pointer to the storage location for time.

Return Value

Return the time as seconds elapsed since midnight, January 1, 1970, or -1 in the case of an error.

Remarks

The time function returns the number of seconds elapsed since midnight (00:00:00), January 1, 1970, Coordinated Universal Time (UTC), according to the system clock. The return value is stored in the location given by timer. This parameter may be NULL, in which case the return value is not stored.

time is a wrapper for _time64 and time_t is, by default, equivalent to __time64_t. If you need to force the compiler to interpret time_t as the old 32-bit time_t, you can define _USE_32BIT_TIME_T. This is not recommended because your application may fail after January 18, 2038; the use of this macro is not allowed on 64-bit platforms.

Requirements

Routine	Required header
`time`, `_time32`, `_time64`	C: <time.h>, C++: <ctime> or <time.h>

For additional compatibility information, see Compatibility in the Introduction.

Example

// crt_times.c  
// compile with: /W3  
// This program demonstrates these time and date functions:  
//      time         _ftime    ctime_s     asctime_s  
//      _localtime64_s    _gmtime64_s    mktime    _tzset  
//      _strtime_s     _strdate_s  strftime  
//  
// Also the global variable:  
//      _tzname  
//  
// Turn off deprecated unsafe CRT function warnings  
#define _CRT_SECURE_NO_WARNINGS 1  
  
#include <time.h>  
#include <stdio.h>  
#include <stdlib.h>  
#include <sys/types.h>  
#include <sys/timeb.h>  
#include <string.h>  
  
int main()  
{  
    char tmpbuf[128], timebuf[26], ampm[] = "AM";  
    time_t ltime;  
    struct _timeb tstruct;  
    struct tm today, gmt, xmas = { 0, 0, 12, 25, 11, 93 };  
    errno_t err;  
  
    // Set time zone from TZ environment variable. If TZ is not set,  
    // the operating system is queried to obtain the default value   
    // for the variable.   
    //  
    _tzset();  
  
    // Display operating system-style date and time.   
    _strtime_s( tmpbuf, 128 );  
    printf( "OS time:\t\t\t\t%s\n", tmpbuf );  
    _strdate_s( tmpbuf, 128 );  
    printf( "OS date:\t\t\t\t%s\n", tmpbuf );  
  
    // Get UNIX-style time and display as number and string.   
    time( &ltime );  
    printf( "Time in seconds since UTC 1/1/70:\t%lld\n", (long long)ltime );  
    err = ctime_s(timebuf, 26, &ltime);  
    if (err)  
    {  
       printf("ctime_s failed due to an invalid argument.");  
       exit(1);  
    }  
    printf( "UNIX time and date:\t\t\t%s", timebuf );  
  
    // Display UTC.   
    err = _gmtime64_s( &gmt, &ltime );  
    if (err)  
    {  
       printf("_gmtime64_s failed due to an invalid argument.");  
    }  
    err = asctime_s(timebuf, 26, &gmt);  
    if (err)  
    {  
       printf("asctime_s failed due to an invalid argument.");  
       exit(1);  
    }  
    printf( "Coordinated universal time:\t\t%s", timebuf );  
  
    // Convert to time structure and adjust for PM if necessary.   
    err = _localtime64_s( &today, &ltime );  
    if (err)  
    {  
       printf("_localtime64_s failed due to an invalid argument.");  
       exit(1);  
    }  
    if( today.tm_hour >= 12 )  
    {  
   strcpy_s( ampm, sizeof(ampm), "PM" );  
   today.tm_hour -= 12;  
    }  
    if( today.tm_hour == 0 )  // Adjust if midnight hour.  
   today.tm_hour = 12;  
  
    // Convert today into an ASCII string   
    err = asctime_s(timebuf, 26, &today);  
    if (err)  
    {  
       printf("asctime_s failed due to an invalid argument.");  
       exit(1);  
    }  
  
    // Note how pointer addition is used to skip the first 11   
    // characters and printf is used to trim off terminating   
    // characters.  
    //  
    printf( "12-hour time:\t\t\t\t%.8s %s\n",  
       timebuf + 11, ampm );  
  
    // Print additional time information.   
    _ftime( &tstruct ); // C4996  
    // Note: _ftime is deprecated; consider using _ftime_s instead  
    printf( "Plus milliseconds:\t\t\t%u\n", tstruct.millitm );  
    printf( "Zone difference in hours from UTC:\t%u\n",   
             tstruct.timezone/60 );  
    printf( "Time zone name:\t\t\t\t%s\n", _tzname[0] ); //C4996  
    // Note: _tzname is deprecated; consider using _get_tzname  
    printf( "Daylight savings:\t\t\t%s\n",   
             tstruct.dstflag ? "YES" : "NO" );  
  
    // Make time for noon on Christmas, 1993.   
    if( mktime( &xmas ) != (time_t)-1 )  
    {  
       err = asctime_s(timebuf, 26, &xmas);  
       if (err)  
       {  
          printf("asctime_s failed due to an invalid argument.");  
          exit(1);  
       }  
       printf( "Christmas\t\t\t\t%s\n", timebuf );  
    }  
  
    // Use time structure to build a customized time string.   
    err = _localtime64_s( &today, &ltime );  
    if (err)  
    {  
        printf(" _localtime64_s failed due to invalid arguments.");  
        exit(1);  
    }  
  
    // Use strftime to build a customized time string.   
    strftime( tmpbuf, 128,  
         "Today is %A, day %d of %B in the year %Y.\n", &today );  
    printf( tmpbuf );  
}

OS time:            13:51:23  
OS date:            04/25/03  
Time in seconds since UTC 1/1/70:   1051303883  
UNIX time and date:         Fri Apr 25 13:51:23 2003  
Coordinated universal time:      Fri Apr 25 20:51:23 2003  
12-hour time:            01:51:23 PM  
Plus milliseconds:         552  
Zone difference in hours from UTC:   8  
Time zone name:            Pacific Standard Time  
Daylight savings:         YES  
Christmas            Sat Dec 25 12:00:00 1993  
  
Today is Friday, day 25 of April in the year 2003.

.NET Framework Equivalent

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

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