putchar('\\') returns single '\' - on windows using mingw

Question

Going through K&R 'The C Programming Language' and on exercise 1-10 where you are asked to replace each tab, backspace, and backslash with two backslashes. I noticed that my console is returning only '\'

example of my code

#include <stdio.h>

main ()
{

 int c;

 while ((c = getchar()) != EOF) {


  switch (c) {
      case '\t': putchar ('\\');  break;
      case ' ': putchar ('\\');  break;
      case '\\': putchar ('\\'); break;
      default:   putchar (c);
  }
 }

}

to fix it I have to put:

  switch (c) {
      case '\t': putchar ('\\'); putchar ('\\') break;

is this something to do with windows and character literals or am I missing something? Just wondering if this is an indication that I need to do some reading on how programming in c is going to be different for me on windows (even using gcc compiler)

even as I type in two forward slashes into this question it's reduced to one after posting, now I'm really confused — Shaun Anderson, Mar 06 '16 at 17:27
`'\\'` is just one backslash character.`'//'` is not a valid character. — Martin Zabel, Mar 06 '16 at 17:31
@MartinZabel Yes it is, although the value is implementation defined and therefore not terribly useful, see http://stackoverflow.com/questions/3960954/c-multicharacter-literal — Cubic, Mar 06 '16 at 17:41

erip · Accepted Answer · 2016-03-06T17:45:56.567

3

You're falling victim to what many in the regex business call blackslash hell.

Because traditionally \ is used to denote escape sequence, escaping it can (understandably) get a little confusing.

For every \ that you want to print, you need to escape it with another \.

display -> write
----------------
  \     -> \\
  \\    -> \\\\

etc. ad nauseum

Unfortunately \\\\ isn't a char, so you won't be able to use putchar, but you'll want 4 slashes. You can use puts("\\\\") or use your current approach with two putchar('\\').

edited Mar 06 '16 at 17:45

answered Mar 06 '16 at 17:30

erip

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thank you for this, especially for taking the time to include a useful article – Shaun Anderson Mar 06 '16 at 17:42

putchar('\\') returns single '\' - on windows using mingw

1 Answers1