Friday, December 30, 2005

Toys for boys

The weather has been kind over Christmas, particularly clear skys for my *new* Meade ETX 105 - that's a telescope by the way. Not exactly the largest - only 4" and yes, size does matter, but I couldn't really justify a larger one given that it usually rains on the rare occasions when I am actually at home.
Good views of Mars in November and early December, now good views of Saturn, and various nebula like M42 and M37. OK, so what's that got to do with programming and stuff?
Well, most modern telescopes have an electronic control called a "goto" system - you get the idea. This is normally controlled by a hand-held device, but can be controlled by a PC using an Open Source object model named ASCOM - Astronomy Common Object Module.
Currently it appears to be written using COM, which of course is proprietry and realistically only runs on one of the many Microsoft operating systems. OK, you can get it to run on others, but would you want to, really?
This is one I will be looking at further.

Wednesday, December 21, 2005

Switching off terminal echo in Perl

A delegate recently asked me how to switch echo off for password prompting. I couldn't remember, I thought it was Term::ReadLine. Actually it is Term::ReadKey - as expected the Perl Cookbook reminded me. Term::ReadKey is not a base module, but is present on ActiveState and Fedora installations, and easily installed from CPAN. Here is a simple script that works on both Linux and Windows (despite what the documentation says) :

use Term::ReadKey;

print 'Password: ';
ReadMode 'noecho';
my $password = ReadLine; # Corrected
ReadMode 'normal';
chomp $password;

print "Password was: $password\n";

Another delegate said something like "I guess another module will replace characters typed with asterisks". Well, that is not so simple. After some experimentation I came up with the following script, which has to use raw terminal input and take iinto account differences between Windows and Unix/Linux:

use Term::ReadKey;
use strict;

local $| = 1;
print 'Password: ';

my $password = '';
my $retn = $^O eq 'MSWin32'?"\r":"\n";

ReadMode 'raw';

while (1)
my $key;
# Loop waiting for a key to be pressed
while (!defined $key)
$key = ReadKey -1;

last if $key eq $retn;
$password .= $key;

print '*';

ReadMode 'normal';
print "\n";

print "Password was: $password\n";

Check the Term::ReadKey documentation for the arguments. Note that I have to wait for a key to be pressed this time, and write an unbuffered '*' (local $| = 1 makes STDOUT unbuffered).