MyShell [line-editing]

**+Azazel+** · 03-25-2008

Hello guys,

Im almost finished with writing my own shell, but I have just one thing to finish off. Currently to get the line that the user types, I do a read(). But I want the user to be able to move the cursor to any letter, erase that letter, change that letter to anything, move to the end of the line (wtih a ctr-letter), move to the beginning of the line (with a ctr-letter), etc.

Im programming on FreeBSD. I already have experience with Termcap and I wrote my own getchar function (which doesnt wait for the user to type enter). But I dont know how to do implement all this. How would I insert a letter? Currently if I erase a letter, it will leave a blank space in the place. Should I store everything in a char * and with each movement/action work with the string?

Im really just looking for advice. No code is necessary

**matsp** · 03-25-2008

There are "escape sequences" for insert/delete char, which deletes and inserts and moves the text after the current position.

The escape sequence should be available in the Termcap data.

--
Mats

**+Azazel+** · 03-25-2008

Aha I see. Yea I found some stuff on inserting/deleting characters with Termcap. I was wondering how would I keep track of the line that was typed? So that I can parse it afterwards.

edit: I also found that there are ANSI escape codes, could I use those and not really use the termcap cursor commands? That way I use Termcap only for showing the characters while the user types them and thats it. Although I might be mistaken :/

**matsp** · 03-25-2008

Well, the ANSI codes only work on an ANSI compatible console, which may not be the case for all console variants. That's why there is a termcap functionality to support multiple hardware variants.

I have written code to read commands, and I just kept the input as a string - then split it when the user hits enter.

--
Mats

**+Azazel+** · 03-26-2008

yea, well you see the thing is:

for it to appear as the user types it, after each my_getchar I do a putchar of that character. Afterwards the user modifies the line, does some inserts or something. Now he presses enter.... How do I get this line?

**brewbuck** · 03-26-2008

That's a very boring wheel to reinvent. Look at the readline library. It allows editing, has configurable key bindings, keeps a history, and support tab-completion.

**+Azazel+** · 03-26-2008

I know I know, but I still want to do it my way. I mean in the end its "my" project so I might as well redo everything. (+ you learn more, I think )

But thanks for the suggestion nevertheless

**brewbuck** · 03-26-2008

Originally Posted by +Azazel+

I know I know, but I still want to do it my way. I mean in the end its "my" project so I might as well redo everything. (+ you learn more, I think )

But thanks for the suggestion nevertheless

Well if you're going to bang on the terminal yourself, at least use termcap instead of hard-coding a bunch of escape sequences. You have to put the terminal in an unbuffered mode, and possibly a raw mode. There's a lot of stuff to do.

**+Azazel+** · 03-26-2008

Yep, I know that. I have already set the terminal into non-canonical mode + I know how to utilise Termcap. All Im really worried about is getting that line which the user will be modifying.

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MyShell [line-editing]