Newbie questions

[Barr, Keith]

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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

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[Dan Zwell]

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

 

[James Edward Gray II]

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 Gray II

 

[William James]

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?

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
}

 

[Bertram Scharpf]

Hi,

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

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

=20
def getkey
select( [$stdin], nil, nil, 0.01 ) ? c =3D $stdin.getc : c =3D nil
end

Why `c=3D=C2=B4? 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


--=20
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de

 

[Wai Tsang]

Hi,

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

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.

 

[William James]

Hi,

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

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

 

[Bertram Scharpf]

Hi,

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

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

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

 

[Bertram Scharpf]

Hi,

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

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

=20
select( [$stdin], nil, nil, 0.01 ) ? c =3D $stdin.getc : c =3D nil

Why `c=3D=C2=B4? Why twice?

=20
It means if select( [$stdin], nil, nil, 0.01 ) return true,
then c =3D $stdin.getc; otherwise c =3D 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


--=20
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de

 

[John Joyce]

Hi,

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

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

select( [$stdin], nil, nil, 0.01 ) ? c =3D $stdin.getc : c =3D = nil
Why `c=3D=B4? Why twice?

It means if select( [$stdin], nil, nil, 0.01 ) return true,
then c =3D $stdin.getc; otherwise c =3D 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 =20
a lie' implies that the person is maliciously trying to spread false =20
information. It might be more appropriate to simply say that it is a =20
mistake and explain why.