From: Heesob Park <phasis@...>
Date: 2009-07-29T13:43:01+09:00
Subject: Re: Ignore F1-F12 keys when user enters text input on console

Hi,

2009/7/29 Deiva Rajasingam <dr.subscribe@gmail.com>:
> I am writing a Ruby script to accept a user's input which will be used
> as a password later on. The user input it taken using STDIN.getc. Since
> it is a password input, when the user enters the characters on the
> keyboard, the entered characters are not displayed and each character is
> obscured by displaying an asterix (*).
>
> The code snippet is shown below.
>
> ---------START---------
> def TestFunc
>  myPassword = ""
>
>  print "Password: "
>  myPassword = getPassword
>
>  print "My password: #{myPassword}\n"
> end
>
> def read_char
>  system "stty raw -echo"
>  ch = STDIN.getc
> ensure
>  system "stty -raw echo"
>  return ch
> end
>
> def getPassword
>  password = ""
>  input = ""
>  isValidLastChar = 1
>  invalidCharacterDetected = 0
>
>  while (password == "") || (password != "" && input != "\r")
>    char = read_char
>    input = char.chr
>    if input == "\r"
>      next
>    end
>
>    if char == 127        # backspace character pressed
>      if password != ""
>        password = password.chop
>        print "\b \b"
>      end
>    elsif input != "" && input[0] > 32 && input[0] < 127
>      print "*"
>      password = password + input
>    end
>  end
>
>  print "\n"
>  return password
> end
> ----------END----------
>
> For this code, if I entered "1234" (without the quotes), followed by the
> F1 key, the PageUp key, the Right arrow key and finally pressed Enter, I
> see the following output on the screen:
>
> -----SCREEN OUTPUT-----
>
> [root@morpheus ~]# irb
> irb(main):001:0> load "TestRuby.rb"
> => true
> irb(main):002:0> testStub
> Password: ***********
> My password: 1234[11~[5~[C
> => nil
> irb(main):004:0>
>
> -----------------------
>
> Observe the printed output.
> 1           -> displayed as 1
> 2           -> displayed as 2
> 3           -> displayed as 3
> 4           -> displayed as 4
> F1          -> displayed as [11~
> PgUp        -> displayed as [5~
> Right arrow -> displayed as [C
>
> I am finding it difficult to figure out a way to ignore/process special
> keys (F1-F12, Up/Down/Left/Right, PgUp, PgDn, Home, End, etc.).
>
> Any suggestions or help?
Try Kernel#select like this:

def read_char
 system "stty raw -echo "
 ch = STDIN.getc
 if ch.chr==27.chr
    STDIN.getc while(select([STDIN],nil,nil,0))
 end
ensure
 system "stty -raw echo "
 return ch
end

Regards,

Park Heesob