asctime
, _wasctime
Convert a tm
time structure to a character string. More secure versions of these functions are available; see asctime_s
, _wasctime_s
.
Syntax
char *asctime(
const struct tm *timeptr
);
wchar_t *_wasctime(
const struct tm *timeptr
);
Parameters
timeptr
Time/date structure.
Return value
asctime
returns a pointer to the character string result; _wasctime
returns a pointer to the wide-character string result. There's no error return value.
Remarks
More secure versions of these functions are available; see asctime_s
, _wasctime_s
.
The asctime
function converts a time stored as a structure to a character string. The timeptr
value is typically obtained from a call to gmtime
or localtime
, which both return a pointer to a tm
structure, defined in TIME.H.
timeptr member |
Value |
---|---|
tm_hour |
Hours since midnight (0-23) |
tm_isdst |
Positive if daylight saving time is in effect; 0 if daylight saving time isn't in effect; negative if status of daylight saving time is unknown. The C run-time library assumes the United States' rules for implementing the calculation of Daylight Saving Time (DST). |
tm_mday |
Day of month (1-31) |
tm_min |
Minutes after hour (0-59) |
tm_mon |
Month (0-11; January = 0) |
tm_sec |
Seconds after minute (0-59) |
tm_wday |
Day of week (0-6; Sunday = 0) |
tm_yday |
Day of year (0-365; January 1 = 0) |
tm_year |
Year (current year minus 1900) |
For information about configuring the local time, see the time
, _ftime
, and localtime
functions. For information about defining the time zone environment and global variables, see the _tzset
function.
The string result produced by asctime
contains exactly 26 characters and has the form Wed Jan 2 02:03:55 1980\n\0
. A 24-hour clock is used. All fields have a constant width. The newline character and the null character occupy the last two positions of the string. asctime
uses a single, statically allocated buffer to hold the return string. Each call to this function destroys the result of the previous call.
_wasctime
is a wide-character version of asctime
, and otherwise behaves identically to asctime
.
These functions validate their parameters. If timeptr
is a null pointer, or if it contains out-of-range values, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, the function returns NULL
and sets 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 mapping
TCHAR.H routine |
_UNICODE and _MBCS not defined |
_MBCS defined |
_UNICODE defined |
---|---|---|---|
_tasctime |
asctime |
asctime |
_wasctime |
Requirements
Routine | Required header |
---|---|
asctime |
<time.h> |
_wasctime |
<time.h> or <wchar.h> |
Example
This program places the system time in the long integer aclock
, translates it into the structure newtime
, and then converts it to string form for output using the asctime
function.
// crt_asctime.c
// compile with: /W3
#include <time.h>
#include <stdio.h>
int main( void )
{
struct tm *newTime;
time_t szClock;
// Get time in seconds
time( &szClock );
// Convert time to struct tm form
newTime = localtime( &szClock );
// Print local time as a string.
printf_s( "Current date and time: %s", asctime( newTime ) ); // C4996
// Note: asctime is deprecated; consider using asctime_s instead
}
Current date and time: Sun Feb 3 11:38:58 2002
See also
Time management
ctime
, _ctime32
, _ctime64
, _wctime
, _wctime32
, _wctime64
_ftime
, _ftime32
, _ftime64
gmtime
, _gmtime32
, _gmtime64
localtime
, _localtime32
, _localtime64
time
, _time32
, _time64
_tzset
asctime_s
, _wasctime_s
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