Take a look at the assoc and ftype commands:

c:\test>assoc .pl
.pl=Perl

c:\test>ftype Perl
Perl="c:\perl\bin\perl.exe" -sw "%1" %*
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They can be used to both query and set the associations and are very easy to drive via backticks.

The alternative is digging around in the registry, which is a pain to do and easy to get wrong.

This seems to give what I want. However (and I know that probably it is very simple
but I am missing something) how do I use these within Perl itself to get
the information I want about other applications?

Do you know about backticks?

Here's a silly example to get you started:

#! perl -slw
use strict;

die "You must supply an extension" unless @ARGV;

for ( @ARGV ) {
    my( $extention, $type ) = split '=', `assoc $_ 2>nul`;
    warn "No association was found for extension '$_'" and next
        unless defined $type;
    chomp $type;

    my( undef, $cmd ) = split '=', `ftype $type 2>nul`;
    warn "No command was associated with type '$type'" and next
        unless defined $cmd;
    chomp $cmd;

    print "Extension '$_' is associated with type '$type' "
    .     "\n\tand the command: '$cmd'";
}
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And an example of using the above code:

c:\test>AssocFtype.pl .pl .doc
Extension '.pl' is associated with type 'Perl'
        and the command: '"c:\perl\bin\perl.exe" -sw "%1" %*'
Extension '.doc' is associated with type 'OpenOffice.org.doc'
        and the command: '"C:\Program Files\OpenOffice.org 2.2\program
+\soffice.exe" -o "%1"'
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---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

In general HKEY_CLASSES_ROOT stores information about registered applications such as file associations.

Win32::TieRegistry lets you fiddle with the registry so in theory no problem. However with the Windows registry it’s always tricky.

I think it depends on the Windows version you run and also on the particular user logged in. Software can be installed for all users or specific user(s), different users can install the same software (or different versions of it) in different locations, etc. The registry follows a strategy for looking up and writing information. You better read Windows_Registry first (fairly good description).

Make sure you BACKUP the registry! It is too easy to screw it up! Also it doesn’t harm to have a regedit/regcleaner nearby;-)

I have looked in the HKEY_CLASSES_ROOT registry.
This seems to have two sections. One for extensions and one for applicatons.
I guessed the extension section would give the path. However I could not see it.
Is this hidden in some way?
The problem with the application section is that I could not see the name of the application I was looking for.

The extensions are there but if you want the path where the application is installed you have to look elsewhere.

An example


On my system: HK_CURRENT_USER\Software\Adobe\Acrobat Reader\7.0\InstallPath

Value: "C:\Program Files\Adobe\Acrobat 7.0\Reader"

If this lookup fails look at HKEY_LOCAL_MACHINE\software\companyname\product. I think this is in general the lookup strategy, i.e. first check HKCU if that fails check HKLM. Like I said it depends on the user logged on. I also recall (on the top of my head) that the registry differs (slightly) between different Windows flavours.

See also Windows registry information for advanced users.

HTH