Linux – Working around a buggy keyboard / hacking an input stream

When you say Function-F1, I assume you mean pressing that funny little Fn key in the corner of a laptop followed by the F1 key at the top left of the keyboard. And that your trying to map one of the extra keys like Sleep that some laptop keyboards have. It looks like that key is literally pressing multiple keys for you. First I see Win+L as one combo. On Windows, this shortcut locks the screen, but does not start the screensaver. Next, I see a mapping for XF86ScreenSaver which might mean that X is seeing some kind of sleep keycode. I'm guessing that that key on your laptop keyboard is physically sending out those three keycodes of Win + L + Sleep as a convenience for Windows users to quickly lock the screen and activate the screensaver. I'm not sure of a good way to filter those out. The Fn key on keyboards normally is not seen by the Linux Kernel. Instead, it changes which codes the keyboard tells the kernel. When I was trying to use a USB RF PowerPoint remote with OOo on Linux, I discovered that the button to start/stop the presentation was just a lame control to send out alternating F5 and ESC key codes. Other buttons were just as lame like sending out b to blank the screen.

I wrote this a long time ago. It's a script that sits between the user's input and an interactive program, and allows the input to be intercepted. I used it to escape to the shell to check filenames when running old Fortran programs that asked lots of questions. You could easily modify it to intercept particular inputs and sanitize them.

#!/usr/bin/perl

# shwrap.pl - Wrap any process for convenient escape to the shell.

use strict;
use warnings;

# Provide the executable to wrap as an argument
my $executable = shift;

my @escape_chars = ('#');             # Escape to shell with these chars
my $exit = 'bye';                     # Exit string for quick termination

open my $exe_fh, "|$executable @ARGV" or die "Cannot pipe to program $executable: $!";

# Set magic buffer autoflush on...
select((select($exe_fh), $| = 1)[0]);

# Accept input until the child process terminates or is terminated...
while ( 1 ) {
   chomp(my $input = <STDIN>);

   # End if we receive the special exit string...
   if ( $input =~ m/$exit/ ) {
      close $exe_fh;
      print "$0: Terminated child process...\n";
      exit;
   }

   foreach my $char ( @escape_chars ) {
      # Escape to the shell if the input starts with an escape character...
      if ( my ($command) = $input =~ m/^$char(.*)/ ) {
         system $command;
      }
      # Otherwise pass the input on to the executable...
      else {
         print $exe_fh "$input\n";
      }
   }
}

A simple example test program you can try it out on:

#!/usr/bin/perl

while (<>) {
   print "Got: $_";
}