_strlwr_s, _strlwr_s_l, _mbslwr_s, _mbslwr_s_l, _wcslwr_s, _wcslwr_s_l

Article
11/16/2012

Convert a string to lowercase, using the current locale or a locale object passed in. These are versions of _strlwr, _wcslwr, _mbslwr, _strlwr_l, _wcslwr_l, _mbslwr_l with security enhancements as described in Security Enhancements in the CRT.

errno_t _strlwr_s(
   char *str,
   size_t numberOfElements
);
errno_t _strlwr_s_l(
   char *str,
   size_t numberOfElements,
   _locale_t locale
);
errno_t _mbslwr_s(
   unsigned char *str,
   size_t numberOfElements
);
errno_t _mbslwr_s_l(
   unsigned char *str,
   size_t numberOfElements,
   _locale_t locale
);
errno_t _wcslwr_s(
   wchar_t *str,
   size_t numberOfElements
);
errno_t _wcslwr_s_l(
   wchar_t *str,
   size_t numberOfElements,
   _locale_t locale
);
template <size_t size>
errno_t _strlwr_s(
   char (&str)[size]
); // C++ only
template <size_t size>
errno_t _strlwr_s_l(
   char (&str)[size],
   _locale_t locale
); // C++ only
template <size_t size>
errno_t _mbslwr_s(
   unsigned char (&str)[size]
); // C++ only
template <size_t size>
errno_t _mbslwr_s_l(
   unsigned char (&str)[size],
   _locale_t locale
); // C++ only
template <size_t size>
errno_t _wcslwr_s(
   wchar_t (&str)[size]
); // C++ only
template <size_t size>
errno_t _wcslwr_s_l(
   wchar_t (&str)[size],
   _locale_t locale
); // C++ only

Parameters

str
Null-terminated string to convert to lowercase.
numberOfElements
Size of the buffer.
locale
The locale to use.

Return Value

Zero if successful; a non-zero error code on failure.

These functions validate their parameters. If str is a NULL pointer, the invalid parameter handler is invoked, as described in Parameter Validation . If execution is allowed to continue, the functions return EINVAL and set errno to EINVAL. If numberOfElements is less than the length of the string, the functions also return EINVAL and set errno to EINVAL.

Remarks

The _strlwr_s function converts, in place, any uppercase letters in str to lowercase. _mbslwr_s is a multi-byte character version of _strlwr_s. _wcslwr_s is a wide-character version of _strlwr_s.

The output value is affected by the setting of the LC_CTYPE category setting of the locale; see setlocale for more information. The versions of these functions without the _l suffix use the current locale for this locale-dependent behavior; the versions with the _l suffix are identical except that they use the locale parameter passed in instead. For more information, see Locale.

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.

The debug versions of these functions first fill the buffer with 0xFD. To disable this behavior, use _CrtSetDebugFillThreshold.

Generic-Text Routine Mappings

TCHAR.H routine	_UNICODE & _MBCS not defined	_MBCS defined	_UNICODE defined
_tcslwr_s	_strlwr_s	_mbslwr_s	_wcslwr_s
_tcslwr_s_l	_strlwr_s_l	_mbslwr_s_l	_wcslwr_s_l

Requirements

Routine	Required header
_strlwr_s, _strlwr_s_l	<string.h>
_mbslwr_s, _mbslwr_s_l	<mbstring.h>
_wcslwr_s, _wcslwr_s_l	<string.h> or <wchar.h>

For additional compatibility information, see Compatibility in the Introduction.

Example

// crt_strlwr_s.cpp
// This program uses _strlwr_s and _strupr_s to create
// uppercase and lowercase copies of a mixed-case string.
//

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

int main()
{
   char str[] = "The String to End All Strings!";
   char *copy1, *copy2;
   errno_t err;

   err = _strlwr_s( copy1 = _strdup(str), strlen(str) + 1);
   err = _strupr_s( copy2 = _strdup(str), strlen(str) + 1);

   printf( "Mixed: %s\n", str );
   printf( "Lower: %s\n", copy1 );
   printf( "Upper: %s\n", copy2 );

   free( copy1 );
   free( copy2 );

   return 0;
}

Mixed: The String to End All Strings! Lower: the string to end all strings! Upper: THE STRING TO END ALL STRINGS!

.NET Framework Equivalent

System::String::ToLower

Smart Device Developer Notes

These methods are provided for Windows CE; however, the underlying CRT method used in CE is currently not secure. Use of these functions is still recommended so that your code can benefit from the secure versions of the methods when those become available.

Change History

Date	History	Reason
December 2009	Corrected the required files list and return values.	Content bug fix.