_strlwr, _wcslwr, _mbslwr, _strlwr_l, _wcslwr_l, _mbslwr_l

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06/05/2017

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Converts a string to lowercase. More secure versions of these functions are available; see _strlwr_s, _strlwr_s_l, _mbslwr_s, _mbslwr_s_l, _wcslwr_s, _wcslwr_s_l.

Important

_mbslwr and _mbslwr_l cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported with /ZW.

Syntax

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.

Return Value

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.

Remarks

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. For more information, see Locale.

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`

Requirements

Routine	Required header
`_strlwr`, `_strlwr_l`	<string.h>
`_wcslwr`, `_wcslwr_l`	<string.h> or <wchar.h>
`_mbslwr`, `_mbslwr_l`	<mbstring.h>

For additional compatibility information, see Compatibility.

Example

// 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 );  
}

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

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