Newbie questions

Ruby
1

Hi there,

I am new to using Ruby and I am writing my first real programs and I
have something I was wonndering about:

I have a menu that I would like users to respond to simply by entering a
single character. I have tried both STDIN.getc and gets, but both
require a carriage return. Is there a command I haven’t found that will
actively read STDIN to process a single character as soon as it is
entered?

Thanks in advance,
Keith

2

Barr, Keith wrote:

Hi there,

I am new to using Ruby and I am writing my first real programs and I have something I was wonndering about:

I have a menu that I would like users to respond to simply by entering a single character. I have tried both STDIN.getc and gets, but both require a carriage return. Is there a command I haven’t found that will actively read STDIN to process a single character as soon as it is entered?

Thanks in advance,
Keith

This is a common question. You need a library (gem) that provides this
function. I have heard that highline, ncurses, and termios have this. In
ncurses, it’s called “getch”, but I don’t know about the others.

Dan

3

On Aug 25, 2007, at 3:36 PM, Dan Z. wrote:

Keith

This is a common question. You need a library (gem) that provides
this function. I have heard that highline, ncurses, and termios
have this. In ncurses, it’s called “getch”, but I don’t know about
the others.

Here’s how you do it with HighLine:

http://blog.grayproductions.net/articles/i_just_want_one_character

James Edward G. II

4

Hi,

Am Sonntag, 26. Aug 2007, 07:00:06 +0900 schrieb William J.:

On Aug 25, 3:05 pm, “Barr, Keith” [email protected] wrote:

I have a menu that I would like users to respond to
simply by entering a single character.

def getkey
select( [$stdin], nil, nil, 0.01 ) ? c = $stdin.getc : c = nil
end

Why `c=´? Why twice?

It doesn’t work here; it still waits for the enter key.

I doubt whether there is any other way than using termios.

Bertram

5

On Aug 25, 3:05 pm, “Barr, Keith” [email protected] wrote:

soon as it is entered?
if RUBY_PLATFORM =~ /win32/
require ‘Win32API’
Kbhit = Win32API.new(“msvcrt”, “_kbhit”, [], ‘I’)
Getch = Win32API.new(“msvcrt”, “_getch”, [], ‘I’)
def getkey
sleep 0.01
return nil if Kbhit.call.zero?
c = Getch.call
c = Getch.call + 256 if c.zero? || c == 0xE0
c
end
else
def getkey
select( [$stdin], nil, nil, 0.01 ) ? c = $stdin.getc : c = nil
end
end

5.times{
begin end until key = getkey
print key.chr
}

6

Bertram S. wrote:

Hi,

Am Sonntag, 26. Aug 2007, 07:00:06 +0900 schrieb William J.:

On Aug 25, 3:05 pm, “Barr, Keith” [email protected] wrote:

I have a menu that I would like users to respond to
simply by entering a single character.

def getkey
select( [$stdin], nil, nil, 0.01 ) ? c = $stdin.getc : c = nil
end

Why `c=´? Why twice?

It doesn’t work here; it still waits for the enter key.

I doubt whether there is any other way than using termios.

Bertram

It means if select( [$stdin], nil, nil, 0.01 ) return true,
then c = $stdin.getc; otherwise c = nil.

7

On Aug 25, 7:16 pm, Bertram S. [email protected] wrote:

end

Why `c=´? Why twice?

Don’t ask me; it’s not my code.

It doesn’t work here; it still waits for the enter key.

It works here under windoze; I can’t test it under unix.

8

Hi,

Am Sonntag, 26. Aug 2007, 15:15:04 +0900 schrieb William J.:

On Aug 25, 7:16 pm, Bertram S. [email protected] wrote:

Am Sonntag, 26. Aug 2007, 07:00:06 +0900 schrieb William J.:

def getkey
select( [$stdin], nil, nil, 0.01 ) ? c = $stdin.getc : c = nil
end

It doesn’t work here; it still waits for the enter key.

It works here under windoze; I can’t test it under unix.

That was what I meant: You did not test it on a POSIX
system.

You wrote:

if RUBY_PLATFORM =~ /win32/
[…]
else
def getkey
select( [$stdin], nil, nil, 0.01 ) ? c = $stdin.getc : c = nil
end
end

As long as there are no parsing errors this alway works
under Windows. I tested it under Linux and there, it doesn’t
work.

Bertram

9

On Aug 26, 2007, at 9:32 AM, Bertram S. wrote:

It means if select( [$stdin], nil, nil, 0.01 ) return true,
then c = $stdin.getc; otherwise c = nil.

The variable c will not be used and the assignment is
mentioned twice. Besides that it is questionable whether an
assignment in a ?: expression will parse how the author
intended.

That the function will return `true’ is just a lie.

Bertram
Bertram, no need for inflamatory statements. Calling something ‘just
a lie’ implies that the person is maliciously trying to spread false
information. It might be more appropriate to simply say that it is a
mistake and explain why.

10

Hi,

Am Sonntag, 26. Aug 2007, 10:05:07 +0900 schrieb Wai T.:

Bertram S. wrote:

Am Sonntag, 26. Aug 2007, 07:00:06 +0900 schrieb William J.:

On Aug 25, 3:05 pm, “Barr, Keith” [email protected] wrote:

select( [$stdin], nil, nil, 0.01 ) ?  c = $stdin.getc : c = nil

Why `c=´? Why twice?

It means if select( [$stdin], nil, nil, 0.01 ) return true,
then c = $stdin.getc; otherwise c = nil.

The variable c will not be used and the assignment is
mentioned twice. Besides that it is questionable whether an
assignment in a ?: expression will parse how the author
intended.

That the function will return `true’ is just a lie.

Bertram