13.17练习题17

#include<stdio.h>
#include <ctype.h>
#include <stdbool.h>


bool test_extension(const char *file_name,
const char *extension);
                    
                    
int main()
{
   const char *file_name = "memo.txt";
   const char *extension = "TXT";
  
   test_extension(file_name,
extension);
}

bool test_extension(const char *file_name,
const char *extension)
{
    const char *s;
    s = file_name;
    int n =0;
    for(;*s != '.';s++){
    }
    s++;

    for(;tolower(*s)==tolower(*extension);s++,extension++)
    {
        if(*s)
        n++;
    }
    if(n==3)
        printf("true");
        else 
        printf("false");
    
}