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_strlwr, _wcslwr, _mbslwr, _strlwr_l, _wcslwr_l, _mbslwr_l 

Convert a string to lowercase. These functions are deprecated because more secure versions are available; see _strlwr_s, _strlwr_s_l, _mbslwr_s, _mbslwr_s_l, _wcslwr_s, _wcslwr_s_l.


char *_strlwr(
   char * str
);
wchar_t *_wcslwr(
   wchar_t * str
);
unsigned char *_mbslwr(
   unsigned char * str
);
char *_strlwr_l(
   char * str,
   _locale_t locale
);
wchar_t *_wcslwr_l(
   wchar_t * str,
   _locale_t locale
);
unsigned char *_mbslwr_l(
   unsigned char * str,
   _locale_t locale 
);
template <size_t size>
char *_strlwr(
   char (&str)[size]
); // C++ only
template <size_t size>
wchar_t *_wcslwr(
   wchar_t (&str)[size]
); // C++ only
template <size_t size>
unsigned char *_mbslwr(
   unsigned char (&str)[size]
); // C++ only
template <size_t size>
char *_strlwr_l(
   char (&str)[size],
   _locale_t locale
); // C++ only
template <size_t size>
wchar_t *_wcslwr_l(
   wchar_t (&str)[size],
   _locale_t locale
); // C++ only
template <size_t size>
unsigned char *_mbslwr_l(
   unsigned char (&str)[size],
   _locale_t locale 
); // C++ only

Parameters

str

Null-terminated string to convert to lowercase.

locale

The locale to use.

Each of these functions returns a pointer to the converted string. Because the modification is done in place, the pointer returned is the same as the pointer passed as the input argument. No return value is reserved to indicate an error.

The _strlwr function converts any uppercase letters in str to lowercase as determined by the LC_CTYPE category setting of the locale. Other characters are not affected. For more information on LC_CTYPE, see setlocale. The versions of these functions without the _l suffix use the current locale for their locale-dependent behavior; the versions with the _l suffix are identical except that they use the locale passed in instead.

The _wcslwr and _mbslwr functions are wide-character and multibyte-character versions of _strlwr. The argument and return value of _wcslwr are wide-character strings; those of _mbslwr are multibyte-character strings. These three functions behave identically otherwise.

If str is a NULL pointer, the invalid parameter handler is invoked, as described in Parameter Validation . If execution is allowed to continue, these functions return the original string and set errno to EINVAL.

In C++, these functions have template overloads that invoke the newer, secure counterparts of these functions. For more information, see Secure Template Overloads.

Generic-Text Routine Mappings
TCHAR.H routine _UNICODE & _MBCS not defined _MBCS defined _UNICODE defined

_tcslwr

_strlwr

_mbslwr

_wcslwr

_tcslwr_l

_strlwr_l

_mbslwr_l

_wcslwr_l

Routine Required header Compatibility

_strlwr, _strlwr_l

<string.h>

Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

_wcslwr, _wcslwr_l

<string.h> or <wchar.h>

Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

_mbslwr, _mbslwr_l

<mbstring.h>

Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

For additional compatibility information, see Compatibility in the Introduction.

// crt_strlwr.c
// compile with: /W3
// This program uses _strlwr and _strupr to create
// uppercase and lowercase copies of a mixed-case string.
#include <string.h>
#include <stdio.h>

int main( void )
{
   char string[100] = "The String to End All Strings!";
   char * copy1 = _strdup( string ); // make two copies
   char * copy2 = _strdup( string );

   _strlwr( copy1 ); // C4996
   // Note: _strlwr is deprecated; consider using _strlwr_s instead
   _strupr( copy2 ); // C4996
   // Note: _strupr is deprecated; consider using _strupr_s instead

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

   free( copy1 );
   free( copy2 );
}

Output

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

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