Question

Here is a sample from Kernighan & Ritchie’s ‘The C Programming Language’:

int getline(char s[], int lim) {    int c, i = 0;     while (--lim > 0; && (c=getchar()) !=EOF && c !='\n')    {       s[i++] = c;    }     if (c =='\n')     {       s[i++] = c;    }     s[i] = '\0';     return i; } 

Why do we should check if c != '\n', despite we use s[i++] = c after that?

Answer 1

The functions reads characters from the standard input until either EOF or a newline characters is found.

The second check ensures that the only newline character is put into the char array. EOF shouldn’t occur in a proper c-string. Also, if the character isn’t newline that means that we might have filled up our c-string, in which case we shouldn’t put any more characters into it.

Notice we still append the ‘\0’. We’ve ensured that theres still room for one more character in our c-string, as we use the pre-fix decrementor, which evaluates before the comparison.