/**原型：int strcmp(const char *s1, const char * s2, size_t n);*用法：#include 
     
      *功能：比较字符串s1和s2的前n个字符。*说明：*   当s1
      
       <0*   当s1=s2时，返回值=0*   当s1>s2时，返回值>0*编程实现strncmp*/#include 
       
        #include 
        
         int _strncmp(const char *s, const char *t, int count){    assert((s != NULL)&&(t != NULL));    if(count == 0)        return 0;    while(count-- && *s && *t && *s == *t)    {        s++;        t++;    }    return (*s - *t);}int main(int args,char ** argv){    char s1[] = "Hello world!";    char s2[] = "Hello World!";    int flag = _strncmp(s1,s2,7);    if(flag < 0)    printf("%s is less than %s\n",s1,s2);    else if(flag == 0)  printf("%s is equal %s\n",s1,s2);    else    printf("%s is larger than %s",s1,s2);    getchar();    return 0;}