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I'm using curses to develop a small console application.

I have a main loop section which waits for user input, it uses the getstr function, of course this waits for the user to press enter.

I would like to capture the up and down and tab keypresses. I suppose this can't be done with getstr.

Anyone have any idea how to do this?

EDIT: I've tried using STDIN.getc wihch blocks the application from running, and getch doesn't catch the arrow keys.

EDIT #2: I'm trying this code on Windows. It seems that Curses.getch works for Linux, but on Windows I get no key sent for the up arrow.

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2 Answers 2

Reset to default
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You need to set the "cbreak" mode of the tty so that you get keypresses immediately. If you don't do this, the Unix terminal-handling system will buffer the input until a newline is received (i.e., the user hits ENTER), and the input will all be handed to the process at that point.

This isn't actually Ruby- or even curses-specific; this is the way all applications work that run through a Unix tty.

Try using the curses library cbreak() function to turn on this mode. Don't forget to call nocbreak() to turn it off before you exit!

For reading a single character, STDIN.getc will return a Fixnum of the ASCII code of the character. Quite possibly you'll find STDIN.read(1) to be more convenient, since it returns a one-character string of the next character.

However, you'll find that the "up/down" keys,if by that you mean the arrow keys, are actually a sequence of characters. On most ANSI-like terminal emulators these days (such as xterm), the up arrow will be "\e[A" (that \e is an escape character) for example. There are termcap (terminal capability) databases to deal with this sort of thing, and you can access them through curses, but intially you may find it easiest just to experiment with interpreting these directly; you're not very likely to run into a terminal using anything other than ANSI codes these days.

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4 Comments

thx for the answer im going to try that now, btw can you tell me what crmode function does?
I'd not heard of crmode and nocrmode, but according to redmine.ruby-lang.org/issues/show/916 , they're just aliases for cbreak and nocbreak (now that the bug is fixed).
then using crmode or cbrak would be the same thing?!.
For some reason when i use STDIN.getc my ruby program wont run, just sits idly there and wont start the application
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you want getch rather than getstr. also see curt sampson's comment about the arrow keys not being a single character.

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7 Comments

getch doesnt catch the arrows, only the TAB
Does it catch an ESC when you press an arrow? If so, you're probably not reading all three characters that get sent when you press an arrow key.
It doesn't catch the arrows, no value is sent on the input
this worked for me, under linux: require 'curses' while true puts Curses.getch end
(okay, looks like comments don't format code at all. you get the general idea though)
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