Uredi

Deli z drugimi prek

ctime, _ctime32, _ctime64, _wctime, _wctime32, _wctime64

  • Članek

Convert a time value to a string and adjust for local time zone settings. More secure versions of these functions are available; see ctime_s, _ctime32_s, _ctime64_s, _wctime_s, _wctime32_s, _wctime64_s.

Syntax

char *ctime( const time_t *sourceTime );
char *_ctime32( const __time32_t *sourceTime );
char *_ctime64( const __time64_t *sourceTime );
wchar_t *_wctime( const time_t *sourceTime );
wchar_t *_wctime32( const __time32_t *sourceTime );
wchar_t *_wctime64( const __time64_t *sourceTime );

Parameters

sourceTime
Pointer to stored time to convert.

Return value

A pointer to the character string result. NULL is returned when:

  • sourceTime represents a date before midnight, January 1, 1970, UTC.

  • You use _ctime32 or _wctime32, and sourceTime represents a date after 23:59:59 January 18, 2038, UTC.

  • You use _ctime64 or _wctime64, and sourceTime represents a date after 23:59:59, December 31, 3000, UTC.

ctime is an inline function that evaluates to _ctime64, and time_t is 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 macro causes ctime to evaluate to _ctime32. We don't recommend you use it, because your application may fail after January 18, 2038, and it isn't allowed on 64-bit platforms.

Remarks

The ctime function converts a time value stored as a time_t value into a character string. The sourceTime value is typically obtained from a call to time, which returns the number of seconds elapsed since midnight (00:00:00), January 1, 1970, coordinated universal time (UTC). The return value string contains exactly 26 characters and has the form:

Wed Jan 02 02:03:55 1980\n\0

A 24-hour clock is used. All fields have a constant width. The newline character ('\n') and the null character ('\0') occupy the last two positions of the string.

The converted character string is also adjusted according to the local time zone settings. For information on configuring the local time, see the time, _ftime, and localtime functions. For details about defining the time zone environment and global variables, see the _tzset function.

A call to ctime modifies the single statically allocated buffer used by the gmtime and localtime functions. Each call to one of these routines destroys the result of the previous call. ctime shares a static buffer with the asctime function. Thus, a call to ctime destroys the results of any previous call to asctime, localtime, or gmtime.

_wctime and _wctime64 are the wide-character version of ctime and _ctime64; returning a pointer to wide-character string. Otherwise, _ctime64, _wctime, and _wctime64 behave identically to ctime.

These functions validate their parameters. If sourceTime is a null pointer, or if the sourceTime value is negative, these functions invoke the invalid parameter handler, as described in Parameter validation. If execution is allowed to continue, the functions return NULL and set errno to EINVAL.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Generic-text routine mappings

TCHAR.H routine _UNICODE and _MBCS not defined _MBCS defined _UNICODE defined
_tctime ctime ctime _wctime
_tctime32 _ctime32 _ctime32 _wctime32
_tctime64 _ctime64 _ctime64 _wctime64

Requirements

Routine Required header
ctime <time.h>
_ctime32 <time.h>
_ctime64 <time.h>
_wctime <time.h> or <wchar.h>
_wctime32 <time.h> or <wchar.h>
_wctime64 <time.h> or <wchar.h>

For more compatibility information, see Compatibility.

Example

// crt_ctime64.c
// compile with: /W3
/* This program gets the current
* time in _time64_t form, then uses ctime to
* display the time in string form.
*/

#include <time.h>
#include <stdio.h>

int main( void )
{
   __time64_t ltime;

   _time64( &ltime );
   printf( "The time is %s\n", _ctime64( &ltime ) ); // C4996
   // Note: _ctime64 is deprecated; consider using _ctime64_s
}

The time is Wed Feb 13 16:04:43 2002

See also

Time management
asctime, _wasctime
ctime_s, _ctime32_s, _ctime64_s, _wctime_s, _wctime32_s, _wctime64_s
_ftime, _ftime32, _ftime64
gmtime, _gmtime32, _gmtime64
localtime, _localtime32, _localtime64
time, _time32, _time64