What does this do : while((c= getchar()) != '\n' && c != EOF);

Question

while((c= getchar()) != '\n' && c != EOF);

I was facing a problem by using gets() to enter strings. I found on google that it was keeping the value of '\n' in the input buffer. I searched here and found the above code to solve my problem. However I don't quite get the hold of it. What does this do ?? Anybody please enlighten me.

No, you need to study C++ by yourself and then post a question here — Marco A., Oct 04 '14 at 12:30
I changed `C++` tag to `C` tag as it\`s pure `C`, not a `C++`. — , Oct 04 '14 at 12:34
@Benio don't do that. As long as it's valid C++ code, it doesn't matter that it's also valid C. And sometimes the difference matters. — Mark Ransom, Oct 04 '14 at 12:37

score 4 · Answer 1 · answered Oct 04 '14 at 12:35

4

An assignment in C++ will also yield the value being assigned. So c= getchar() is reading the next character from the file, and (c= getchar()) != '\n' is comparing that read character to the newline character. There's another test for the special EOF value, to make sure it doesn't keep trying to read once you reach the end of the file.

There's no statement between the while and the closing semicolon because nothing else needs to be done, you're throwing the input away.

answered Oct 04 '14 at 12:35

Mark Ransom

299,747
42
398
622

So basically what it does is that after I input the string, it reads the string until it finds a new line character and EOF ie -1 ?? – Adi Oct 04 '14 at 12:42
3

@gotolabeladi Until it finds a new line character ***or*** EOF. – Boann Oct 04 '14 at 14:13

score 2 · Answer 2 · edited Oct 04 '14 at 13:13

2

The code introduces a while-loop. Its exit condition assigns the integer c the value that getchar() returns, and checks whether it is equal to the newline character ('\n') or EOF. If it is, the loop exits. If it isn't, the next character is extracted, and so on.

The code basically skips all characters until the next newline or EOF is reached. It is equivalent to:

for (;;)
{
    c = getchar(); // c has been declared elsewhere
    if (c == '\n' || c == EOF)
        break;
}

edited Oct 04 '14 at 13:13

Lightness Races in Orbit

378,754
76
643
1,055

answered Oct 04 '14 at 12:35

Columbo

60,038
8
155
203

Yeah ! It's much easier to understand this way, than that which was condensed into a single line. +1 – Adi Oct 04 '14 at 12:46
@gotolabeladi , You don't have enough rep to upvote/+1 but you can still accept it – Spikatrix Oct 04 '14 at 13:03

What does this do : while((c= getchar()) != '\n' && c != EOF);

2 Answers2