Poll STDIN for waiting input on Win32

[Bill Atkins]

How can I determine if there's input waiting on STDIN before calling
gets? This code doesn't do the trick:

----

while true
r, w, e =3D select [$stdin], [], [], 1
=20
if r and r.include? $stdin
puts "READY TO READ!"
end
end

-----

Apparently, r always includes $stdin, so it just continuously prints
"READY TO READ".

--=20
Bill Atkins

 

[Bill Kelly]

Hi,

How can I determine if there's input waiting on STDIN before
calling gets?

<laugh> I just posted this a minute ago on the
Threading+TCPServer thread; if I'd seen your message
I'd have posted here instead...

I use:

if WINDOWS_VERSION
require 'dl'
$win32_console_kbhit = Win32API.new("msvcrt", "_kbhit", [], 'I')
def console_input_ready?
$win32_console_kbhit.call != 0
end
else
def console_input_ready?
select([$stdin], nil, nil, 0) != nil
end
end

Note that if you do a gets() when console_input_ready?
is true, you'll still block until the user hits <enter>.

BTW, I was using:

WINDOWS_VERSION = (RUBY_PLATFORM =~ /win32/) != nil


Regards,

Bill

 

[Dale Martenson]

---- Original message from Bill Kelly on 8/9/2005 10:25 AM:

How can I determine if there's input waiting on STDIN before
calling gets?

I use:

if WINDOWS_VERSION
require 'dl'
$win32_console_kbhit = Win32API.new("msvcrt", "_kbhit", [], 'I')
def console_input_ready?
$win32_console_kbhit.call != 0
end
else
def console_input_ready?
select([$stdin], nil, nil, 0) != nil
end
end

Note that if you do a gets() when console_input_ready?
is true, you'll still block until the user hits <enter>.

BTW, I was using:

WINDOWS_VERSION = (RUBY_PLATFORM =~ /win32/) != nil

You can also define '_getch' to allow you to get the character right
away and not have to wait for the user to press the <enter> key.

require 'Win32API'

$win32_console_kbhit = Win32API.new("msvcrt", "_kbhit", [], 'I')
$win32_console_cputs = Win32API.new("msvcrt", "_cputs", ['P'], 'I')
$win32_console_getch = Win32API.new("msvcrt", "_getch", [], 'I')

def console_input_ready?
$win32_console_kbhit.call != 0
end

def console_input
$win32_console_getch.call
end

def console_output( str )
$win32_console_cputs.call( str )
end

while true
if console_input_ready? then
ch = console_input
print "ch: <#{ch.chr}>\n"
break
else
console_output( "." )
sleep 0.5
end
end