IO#getc behavior

[Jon A. Lambert]

I'm writing a console application with an input loop like the following:

while running
keyhit = select( [$stdin], nil, nil, 0.1 )
if keyhit
c = $stdin.getc
session.message(c.chr)
end
end

In the cygwin version of Ruby all is fine. The user hits a key select()
indicates it and the character is gotten with $stdin.getc.

However I ran this under the msvc version of windows and what happens is
select() returns a ready state for $stdin whether a key is hit or not.
Then getc() blocks? because there's nothing yet to be gotten. Worse no I/O
seems to be going on until the user hits the return key and then whammo I
see either the end result of the loops or it appears more likely getc blocks
internally under cover until it sees a CR in the stream.

Is there a workaround?

Thanks

 

[Sean O'Halpin]

Hi Jon,

this is what I use:

--- CODE ---
##
# getch and kbhit for win32
# Sean O'Halpin
#
require 'dl/import'
module Win32API
extend DL::Importer

dlload 'crtdll.dll'

##
# kbhit - returns 0 if nothing waiting, non-zero otherwise
#
extern 'int _kbhit()', :stdcall

##
# getch - blocks waiting for one character of input from console
# Note: returns integer representing character
# Use getch.chr to get one character string
#
extern 'int _getch()', :stdcall

alias :kbhit :_kbhit
alias :getch :_getch

module_function :kbhit, :getch
end

if __FILE__ =3D=3D $0

puts "kbhit"
puts "Hit any key"

while true
x =3D Win32API.kbhit
if x > 0
puts Win32API.getch.chr
break
else
print "."
end
end
end
--- END CODE ---

HTH,

Sean

 

[Tanaka Akira]

However I ran this under the msvc version of windows and what happens is
select() returns a ready state for $stdin whether a key is hit or not.
Then getc() blocks? because there's nothing yet to be gotten. Worse no I/O
seems to be going on until the user hits the return key and then whammo I
see either the end result of the loops or it appears more likely getc blocks
internally under cover until it sees a CR in the stream.

Is there a workaround?

I heard Ruby 1.9 is improved recently. See [ruby-talk:156899].