From: Thorsten Haude <ruby@...>
Date: 2006-07-07T06:58:05+09:00
Subject: ruby-termios

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Hi,

I wrote a program on Linux using ruby-termios which was supposed to run on
Solaris 9. Short description: It doesn't.

Long description: I use ruby-termios to change some terminal settings for
my simple user interface, a menu in this case. It looks like this:

    def fetch
        letter =3D nil

        print @data['text']
        menuMode {
            letter =3D $stdin.readchar.chr
            until @data['options'].include?(letter.upcase) do
                letter =3D $stdin.readchar.chr
            end
        }

        return letter
    end

In this part, @data['text'] contains a menu text, @data['options'] is a
list of valid characters. Here is the termios part of the code:

    def menuMode
        term =3D Termios::getattr($stdin)
        oldterm =3D term

        term.c_lflag &=3D ~(Termios::ECHO | Termios::ICANON)
=20
        Termios::setattr($stdin, Termios::TCSANOW, term)

        yield

        Termios::setattr($stdin, Termios::TCSANOW, oldterm)
        Termios::flush($stdin, Termios::TCIOFLUSH)
    end

The result on Linux is what I expected: I get the characters one by one and
can work on them before they are displayed or in any buffer I care for.

Some strange things happen on Solaris: First of all, my debugging shows
that something changes the termios flags where I don't expect it:

    def menuMode
        term =3D Termios::getattr($stdin)
        oldterm =3D term
        @logger.debug("c_lflag is #{term.c_lflag}")

        term.c_lflag &=3D ~(Termios::ECHO | Termios::ICANON)
=20
        Termios::setattr($stdin, Termios::TCSANOW, term)

        yield

        @logger.debug("c_lflag is #{oldterm.c_lflag}")
        Termios::setattr($stdin, Termios::TCSANOW, oldterm)
        Termios::flush($stdin, Termios::TCIOFLUSH)
    end

Here is a fragment from the logfile:

D, [2006-06-13T15:45:23.732487 #18771] DEBUG -- : c_lflag is 35387
D, [2006-06-13T15:45:29.987362 #18771] DEBUG -- : c_lflag is 35377

Why are the two flags different?


Second, some buffering is going on. If I enter a character, the program
blocks at the readchar. If I run this version of fetch()

     1      def fetch
     2          letter =3D nil
      =20
     3          print @data['text']
     4          menuMode {
     5              @logger.debug("Enter yielded block")
     6              letter =3D $stdin.readchar.chr
     7              @logger.debug("Read in letter '#{letter}'")
      =20
     8              until @data['options'].include?(letter.upcase) do
     9                  @logger.debug("Enter loop block")
    10                  letter =3D $stdin.readchar.chr
    11                  @logger.debug("Read in letter '#{letter}'")
    12              end
    13          }
      =20
    14          return letter
    15      end

=2E..the program blocks at lines 6 and 10 until I enter four characters. Th=
en
all input is passed to the program, so for an invalid character the result
looks like this:

D, [2006-06-13T15:55:09.230396 #19028] DEBUG -- : Enter yielded block
D, [2006-06-13T15:55:13.383131 #19028] DEBUG -- : Read in letter 't'
D, [2006-06-13T15:55:13.383816 #19028] DEBUG -- : Enter loop block
D, [2006-06-13T15:55:13.384062 #19028] DEBUG -- : Read in letter 't'
D, [2006-06-13T15:55:13.384284 #19028] DEBUG -- : Enter loop block
D, [2006-06-13T15:55:13.384498 #19028] DEBUG -- : Read in letter 't'
D, [2006-06-13T15:55:13.384710 #19028] DEBUG -- : Enter loop block
D, [2006-06-13T15:55:13.384918 #19028] DEBUG -- : Read in letter 't'
D, [2006-06-13T15:55:13.385132 #19028] DEBUG -- : Enter loop block

For valid character this means that the first chracter picks a menu option
and the next three characters are entered in whatever is behind that menu
option. Nearly unusable and pretty dangerous.


At the moment I don't know where to look next. It may be some simple
omission, but I can't find it, so any ideas are appreciated. Please let me
know if you need any other information, the debugging is a bit awkward, but
I didn't dare to call the debugger with broken terminal.


Thanks in advance!


Thorsten                             Radiohead: Subterranean Homesick Alien
--=20
Be alert - Some terrorists look normal.

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