_strtime_s, _wstrtime_s

Artigo
06/05/2017

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The latest version of this topic can be found at _strtime_s, _wstrtime_s.

Copy the current time to a buffer. These are versions of _strtime, _wstrtime with security enhancements as described in Security Features in the CRT.

Syntax

errno_t _strtime_s(  
   char *buffer,  
   size_t numberOfElements  
);  
errno_t _wstrtime_s(  
   wchar_t *buffer,  
   size_t numberOfElements  
);  
template <size_t size>  
errno_t _strtime_s(  
   char (&buffer)[size]  
); // C++ only  
template <size_t size>  
errno_t _wstrtime_s(  
   wchar_t (&buffer)[size]  
); // C++ only

Parameters

[out] buffer
A buffer, at least 10 bytes long, where the time will be written.

[in] numberOfElements
The size of the buffer.

Return Value

Zero if successful.

If an error condition occurs, the invalid parameter handler is invoked, as described in Parameter Validation. The return value is an error code if there is a failure. Error codes are defined in ERRNO.H; see the following table for the exact errors generated by this function. For more information on error codes, see errno Constants.

Error Conditions

`buffer`	`numberOfElements`	Return	Contents of `buffer`
`NULL`	(any)	`EINVAL`	Not modified
Not `NULL` (pointing to valid buffer)	0	`EINVAL`	Not modified
Not `NULL` (pointing to valid buffer)	0 < size < 9	`EINVAL`	Empty string
Not `NULL` (pointing to valid buffer)	Size > 9	0	Current time formatted as specified in the remarks

Security Issues

Passing in an invalid non-NULL value for the buffer will result in an access violation if the numberOfElements parameter is greater than 9.

Passing a value for numberOfElements that is greater than the actual size of the buffer will result in buffer overrun.

Remarks

These functions provide more secure versions of _strtime and _wstrtime. The _strtime_s function copies the current local time into the buffer pointed to by timestr. The time is formatted as hh:mm:ss where hh is two digits representing the hour in 24-hour notation, mm is two digits representing the minutes past the hour, and ss is two digits representing seconds. For example, the string 18:23:44 represents 23 minutes and 44 seconds past 6 P.M. The buffer must be at least 9 bytes long; the actual size is specified by the second parameter.

_wstrtime is a wide-character version of _strtime; the argument and return value of _wstrtime are wide-character strings. These functions behave identically otherwise.

In C++, using these functions is simplified by template overloads; the overloads can infer buffer length automatically (eliminating the need to specify a size argument) and they can automatically replace older, non-secure functions with their newer, secure counterparts. For more information, see Secure Template Overloads.

Generic-Text Routine Mapping:

TCHAR.H routine	_UNICODE & _MBCS not defined	_MBCS defined	_UNICODE defined
`_tstrtime_s`	`_strtime_s`	`_strtime_s`	`_wstrtime_s`

Requirements

Routine	Required header
`_strtime_s`	<time.h>
`_wstrtime_s`	<time.h> or <wchar.h>

For additional compatibility information, see Compatibility in the Introduction.

Example

// strtime_s.c  
  
#include <time.h>  
#include <stdio.h>  
  
int main()  
{  
    char tmpbuf[9];  
    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.   
    err = _strtime_s( tmpbuf, 9 );  
    if (err)  
    {  
       printf("_strdate_s failed due to an invalid argument.");  
      exit(1);  
    }  
    printf( "OS time:\t\t\t\t%s\n", tmpbuf );  
    err = _strdate_s( tmpbuf, 9 );  
    if (err)  
    {  
       printf("_strdate_s failed due to an invalid argument.");  
       exit(1);  
    }  
    printf( "OS date:\t\t\t\t%s\n", tmpbuf );  
  
}

OS time:            14:37:49  
OS date:            04/25/03

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