scanf and strcmp with c string

问题

I found a nice example of how to use strcmp, but it's only working with fgets(), and i need to make it work with scanf. So, here's the code:

int main(void) {
char fruit[] = "apple\n";
  char ans[80];
  do {
     printf ("Guess my favorite fruit? ");
     scanf ("%s",ans);
  } while (strcmp (fruit, ans) != 0);
  puts ("Correct answer!");
  return 0;
}

Even when I write the correct answear ("apple") it stays in the loop and keeps asking me what is the favorite fruit... I'm guessing it has something to do with the chars that are not written at ans[80](I need it to be a char array with 80chars at max). I'm not getting this...

Thanks in advance.

回答1:

Scanf will ignore "\n", so you should init char fruit[] = "apple", since ans will never end with '\n'.

P.S: An explain for scanf: Any number of non-whitespace characters, stopping at the first whitespace character found. A terminating null character is automatically added at the end of the stored sequence.

回答2:

scanf() does not write the trailing newline character(s) into ans. strcmp() does consider newline characters in its comparison, so it's not matching your literal, which includes the newline.

回答3:

"scanf" does take newline "\n" character as input. So you are not able to equal the both strings. if you want to equal both strings you need to remove newline"\n" form the first string ("apple" is fine).

来源：https://stackoverflow.com/questions/20792246/scanf-and-strcmp-with-c-string