What do \t and \b do?

Question

I expect this simple line of code

printf("foo\b\tbar\n"); 

to replace "o" with "\t" and to produce the following output

fo     bar 

(assuming that tab stop occurs every 8 characters). On the contrary I get

foo    bar 

It seems that my shell interprets \b as "move the cursors one position back" and \t as "move cursor to the next tab stop". Is this behaviour specific to the shell in which I'm running the code? Should I expect different behaviour on different systems?

Answer 1

No, that's more or less what they're meant to do.

In C (and many other languages), you can insert hard-to-see/type characters using \ notation:

• \a is alert/bell
• \b is backspace/rubout
• \n is newline
• \r is carriage return (return to left margin)
• \t is tab

You can also specify the octal value of any character using \0nnn, or the hexadecimal value of any character with \xnn.

• EG: the ASCII value of _ is octal 137, hex 5f, so it can also be typed \0137 or \x5f, if your keyboard didn't have a _ key or something. This is more useful for control characters like NUL (\0) and ESC (\033)

As someone posted (then deleted their answer before I could +1 it), there are also some less-frequently-used ones:

• \f is a form feed/new page (eject page from printer)
• \v is a vertical tab (move down one line, on the same column)

On screens, \f usually works the same as \v, but on some printers/teletypes, it will go all the way to the next form/sheet of paper.