edit a body of text from the command line in C

Answer 1

I wrote a text editor.

I've been doing C for twenty years.

The data structure for the text was the most complex single data structure I have ever written; this being a data structure which can, as you specify, efficiently handle arbitrary length text.

If you are new to C, you are biting off more than you can chew.

I suggest a simple data structure, like a buffer or linked list - you can't handle arbitrary length text, but it's better than nothing.

Answer 2

That is highly related to the system (OS). I think you are trying to do this on Windows.

You can use the Windows Console API to do it.

If you want to study some libraries for reference (before you roll your own), a good library is the GNU Readline.

Answer 3

You say you want to avoid using libraries (standard or otherwise), but unfortunately in C all input & output is performed via libraries - the language itself has absolutely no input/output facilities.

So you are doomed to use libraries of some sort. Given that you seem to want a textual interface, I suggest vtaking a look at the portable version of curses at http://pdcurses.sourceforge.net.

Answer 4

There is no way in ANSI C to make a portable line-editor. If you roll your own, you will have to reroll it for every new operating system you want your program to work on.

If I may make a suggestion, I would use a pre-existing library to do all of that hard, platform-specific dirty work, and with that leg-up, learn how to handle things like arbitrary-length input and such. Then, when your code works (and is good), learn how to do all that dirty work, and take away the library-crutch. That way, you're not tackling the whole thing - you're breaking it down into more manageable parts.

Even this is a bit of an oversimplification. It took me quite a while to learn how to handle arbitrary-length input.

Also, know that, if you want your code to be portable, removing the library dependency will mean that, if you want to port it, you'll have to either a) rewrite all that dirty-work code, or b) add the library back in.

To end this all on a joke, this is your brain with libraries:

Pigmaei gigantum humeris impositi plusquam ipsi gigantes vident.
(If I have seen a little further it is by standing on the shoulders of Giants.)
--Isaac Newton

This is your brain without libraries:

If I have not seen as far as others, it is because giants were standing on my shoulders.
--Hal Abelson

Answer 5

As for holding the data, I'm guessing that a rope'd be the best data structure available: In a simplified form, it's a tree of strings. When you want to print it on-screen, all you should need to do is walk it in pre-order, and print it. Splitting a line in two involves a relatively simple tree op: add a leaf. The hard part would be in splitting the string itself (copy the string, set the old end to 0, add the leaf, add the pointer)...

Now, there's the issue of tracking the cursor... you could leave a breadcrumb trail to follow from the root to where the cursor currently is.

There's also thinking about a resizable console... that is, if you want your editor to work whether the terminal is 80 or 200 chars wide...