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

[Deiva Rajasingam]

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?

 

[Deiva Rajasingam]

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

Replace
def TestFunc
with
def testFunc

-DR

 

[Heesob Park]

Hi,

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
=C2=A0myPassword =3D ""

=C2=A0print "Password: "
=C2=A0myPassword =3D getPassword

=C2=A0print "My password: #{myPassword}\n"
end

def read_char
=C2=A0system "stty raw -echo"
=C2=A0ch =3D STDIN.getc
ensure
=C2=A0system "stty -raw echo"
=C2=A0return ch
end

def getPassword
=C2=A0password =3D ""
=C2=A0input =3D ""
=C2=A0isValidLastChar =3D 1
=C2=A0invalidCharacterDetected =3D 0

=C2=A0while (password =3D=3D "") || (password !=3D "" && input !=3D "\r")
=C2=A0 =C2=A0char =3D read_char
=C2=A0 =C2=A0input =3D char.chr
=C2=A0 =C2=A0if input =3D=3D "\r"
=C2=A0 =C2=A0 =C2=A0next
=C2=A0 =C2=A0end

=C2=A0 =C2=A0if char =3D=3D 127 =C2=A0 =C2=A0 =C2=A0 =C2=A0# backspace ch= aracter pressed
=C2=A0 =C2=A0 =C2=A0if password !=3D ""
=C2=A0 =C2=A0 =C2=A0 =C2=A0password =3D password.chop
=C2=A0 =C2=A0 =C2=A0 =C2=A0print "\b \b"
=C2=A0 =C2=A0 =C2=A0end
=C2=A0 =C2=A0elsif input !=3D "" && input[0] > 32 && input[0] < 127
=C2=A0 =C2=A0 =C2=A0print "*"
=C2=A0 =C2=A0 =C2=A0password =3D password + input
=C2=A0 =C2=A0end
=C2=A0end

=C2=A0print "\n"
=C2=A0return 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"
=3D> true
irb(main):002:0> testStub
Password: ***********
My password: 1234[11~[5~[C
=3D> nil
irb(main):004:0>

-----------------------

Observe the printed output.
1 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 -> displayed as 1
2 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 -> displayed as 2
3 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 -> displayed as 3
4 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 -> displayed as 4
F1 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0-> displayed as [11~
PgUp =C2=A0 =C2=A0 =C2=A0 =C2=A0-> 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 =3D STDIN.getc
if ch.chr=3D=3D27.chr
STDIN.getc while(select([STDIN],nil,nil,0))
end
ensure
system "stty -raw echo "
return ch
end

Regards,

Park Heesob

 

[Deiva Rajasingam]

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.