strncmp ( )【C语言库函数源代码】

【C语言库函数源代码】

【本程序在Dev C++ 4.9.9.2 下编译通过】

/*

   Compares two strings for lexical order. 

   The comparison stops after: (1) a difference between the strings is found, (2) the end of the strings is reached, or (3) count characters have been compared.

   比较字符串first和last的前n个字符。first > last ,>0;first = last,=0;first < last, <0 。

*/

int my_strncmp(const char *first,const char *last,int count)

{

   if (!count)

      return(0);

   while (--count && *first && *first == *last)first++,last++;

   return( *(unsigned char *)first - *(unsigned char *)last );

}

void Print(char * str1,char *str2,int t,int n)

{

   char *p;

   p = str1;

   while(*p && (p-str1) < n) printf("%c",*p),p++;

   if(t > 0)

        printf("\tUpper Than\t");

     

   else if(t < 0)

      printf("\tLower Than\t");

   else

      printf("\tEqual\t\t");

   p = str2;

   while(*p && (p-str2) < n) printf("%c",*p),p++;

   printf("\n");

}

#define nn 3 

int main()

{

   char *str1= "ammana";

   char *str2 = "babi";

 

   Print(str1,str2,my_strncmp(str1,str2,nn),nn);

   Print(str2,str1,my_strncmp(str2,str1,nn),nn);

   Print(str2,str2,my_strncmp(str2,str2,nn),nn);

  

   system("pause");

   return 0;

}