From: Deiva Rajasingam <dr.subscribe@...>
Date: 2009-07-29T12:12:37+09:00
Subject: Ignore F1-F12 keys when user enters text input on console

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?
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