How come \b is not recognized from ex. 1-10 in K&R?

Question

#include <stdio.h>
/* replace tabs and backspaces with visible characters */

main()

{
    int c;

    while ((c = getchar()) != EOF) {
        if (c == '\t')
            printf("\\t");
        if (c == '\b')
            printf("\\b");
        if (c == '\\')
            printf("\\\\");
        if (c != '\b')
            if (c != '\t')
                if (c != '\\')
                    putchar(c);
    }
}

Why was I not able to see \b backspace signature when I press the backspace?

a couple of comments on your code: `getchar` is evil, conditions with side-effets are evil, and if cascades are evil as well (if they can be conveniently replaced by switch/case statements, which is the `case` here. :D (pun intended) — Andreas Grapentin, Jan 08 '13 at 10:37

score 1 · Answer 1 · answered Jan 08 '13 at 10:26

You need to learn about else, that if-ladder is pretty scary.

And your terminal probably doesn't send a single backspace character, it can be a bit complicated how actual terminal programs represent that kind of "special" key (delete is another favorite).

score 1 · Answer 2 · answered Jan 08 '13 at 10:27

1

If you're on a unix-like system, you probably want to read this: http://en.wikipedia.org/wiki/Cooked_mode

On other operating systems, I don't know, but they are also likely to do things to your input.

answered Jan 08 '13 at 10:27

Art

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score 1 · Answer 3 · edited May 23 '17 at 12:27

1

Some of the characters handled by Terminal. So you can't get control over it. Check this answer.

I tried in my MAC terminal. But i didn't get the value 127 or 8 like, in this answer. I got 32 for backspace character. So when i tried the if condition with 32, it printed out the \b value.

if (c == 32 || c == 8)
    printf("\\b");

edited May 23 '17 at 12:27

Community

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answered Jan 08 '13 at 10:41

arthankamal

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How come \b is not recognized from ex. 1-10 in K&R?

3 Answers3