Ignore F1-F12 keys when user enters text input on console

Ruby
1

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?

2

Sorry a small correction. The test function definition line should be
changed.

Replace
def TestFunc
with
def testFunc

-DR

3

Hi,

2009/7/29 Deiva R. [email protected]:

 myPassword = “”
ensure
 while (password == “”) || (password != “” && input != “\r”)
   end

Password: ***********
4 Â Â Â Â Â → displayed as 4
F1 Â Â Â Â Â → 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 H.

4

Heesob P. wrote:

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

Excellent! It works like a charm. Thanks a bunch. :slight_smile: