Tóm Tắt

`strncmp`, `wcsncmp`, `_mbsncmp`, `_mbsncmp_l`

Bài viết
08/03/2021
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Compares up to the specified count of characters of two strings.

Important

_mbsncmp and _mbsncmp_l cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported in Universal Windows Platform apps.

Syntax

int strncmp(
   const char *string1,
   const char *string2,
   size_t count
);
int wcsncmp(
   const wchar_t *string1,
   const wchar_t *string2,
   size_t count
);
int _mbsncmp(
   const unsigned char *string1,
   const unsigned char *string2,
   size_t count
);
int _mbsncmp_l(
   const unsigned char *string1,
   const unsigned char *string2,
   size_t count,
   _locale_t locale
);int _mbsnbcmp(
   const unsigned char *string1,
   const unsigned char *string2,
   size_t count
);

Parameters

string1, string2
Strings to compare.

count
Number of characters to compare.

locale
Locale to use.

Return Value

The return value indicates the relation of the substrings of string1 and string2 as follows.

Return value
Description

< 0
string1 substring less than string2 substring

0
string1 substring identical to string2 substring

> 0
string1 substring greater than string2 substring

On a parameter validation error, _mbsncmp and _mbsncmp_l return **_NLSCMPERROR**, which is defined in <string.h> and <mbstring.h>.

Remarks

The strncmp function performs an ordinal comparison of at most the first count characters in string1 and string2 and returns a value indicating the relationship between the substrings. strncmp is a case-sensitive version of _strnicmp. wcsncmp and _mbsncmp are case-sensitive versions of _wcsnicmp and _mbsnicmp.

wcsncmp and _mbsncmp are wide-character and multibyte-character versions of strncmp. The arguments of wcsncmp are wide-character strings; those of _mbsncmp are multibyte-character strings. _mbsncmp recognizes multibyte-character sequences according to a multibyte code page and returns _NLSCMPERROR on an error.

Also, _mbsncmp and _mbsncmp_l validate parameters. If string1 or string2 is a null pointer and count is not equal to 0, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, _mbsncmp and _mbsncmp_l return _NLSCMPERROR and set errno to EINVAL. strncmp and wcsncmp do not validate their parameters. These functions behave identically otherwise.

The comparison behavior of _mbsncmp and _mbsncmp_l is affected by the setting of the LC_CTYPE category setting of the locale. This controls detection of leading and trailing bytes of multibyte characters. For more information, see setlocale. The _mbsncmp function uses the current locale for this locale-dependent behavior. The _mbsncmp_l function is identical except that it uses the locale parameter instead. For more information, see Locale. If the locale is a single-byte locale, the behavior of these functions is identical to strncmp.

By default, this function’s global state is scoped to the application. To change this, see Global state in the CRT.

Generic-Text Routine Mappings

TCHAR.H routine
_UNICODE & _MBCS not defined
_MBCS defined
_UNICODE defined

_tcsnccmp
strncmp
_mbsncmp
wcsncmp
_tcsncmp
strncmp
_mbsnbcmp
wcsncmp
_tccmp
Maps to macro or inline function
_mbsncmp
Maps to macro or inline function

not applicable
not applicable
_mbsncmp_l
not applicable

Requirements

Routine
Required header

strncmp
<string.h>
wcsncmp
<string.h> or <wchar.h>
_mbsncmp, _mbsncmp_l
<mbstring.h>

For additional compatibility information, see Compatibility.

Example

// crt_strncmp.c
#include <string.h>
#include <stdio.h>

char string1[] = "The quick brown dog jumps over the lazy fox";
char string2[] = "The QUICK brown fox jumps over the lazy dog";

int main( void )
{
   char tmp[20];
   int result;
   printf( "Compare strings:\n      %s\n      %s\n\n",
           string1, string2 );
   printf( "Function:   strncmp (first 10 characters only)\n" );
   result = strncmp( string1, string2 , 10 );
   if( result > 0 )
      strcpy_s( tmp, sizeof(tmp), "greater than" );
   else if( result < 0 )
      strcpy_s( tmp, sizeof(tmp), "less than" );
   else
      strcpy_s( tmp, sizeof(tmp), "equal to" );
   printf( "Result:      String 1 is %s string 2\n\n", tmp );
   printf( "Function:   strnicmp _strnicmp (first 10 characters only)\n" );
   result = _strnicmp( string1, string2, 10 );
   if( result > 0 )
      strcpy_s( tmp, sizeof(tmp), "greater than" );
   else if( result < 0 )
      strcpy_s( tmp, sizeof(tmp), "less than" );
   else
      strcpy_s( tmp, sizeof(tmp), "equal to" );
   printf( "Result:      String 1 is %s string 2\n", tmp );
}

Compare strings:
      The quick brown dog jumps over the lazy fox
      The QUICK brown fox jumps over the lazy dog

Function:   strncmp (first 10 characters only)
Result:      String 1 is greater than string 2

Function:   strnicmp _strnicmp (first 10 characters only)
Result:      String 1 is equal to string 2

strncmp, wcsncmp, _mbsncmp, _mbsncmp_l