Date: Tue, 13 Oct 1998 18:07:10 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender: eliz AT is
To: Endlisnis <s257m AT unb DOT ca>
cc: djgpp AT delorie DOT com
Subject: Re: Uninstaller.
In-Reply-To: <361BD7AD.81EBE42A@unb.ca>
Message-ID: <Pine.SUN.3.91.981013180650.4278V-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Reply-To: djgpp AT delorie DOT com


On Wed, 7 Oct 1998, Endlisnis wrote:

> What if LFN is disabled?  How do I know what filename will change
> to?

If it is disabled in the environment, just push LFN=y into the
environment at the beginning of your program:

	    putenv ("LFN=y");

However, if it is disabled via the Windows Control Panel, or if your
program runs in plain DOS mode on a machine where the package being
uninstalled was used under Windows, then the bad news are you don't
have any way to know what are the short 8+3 aliases of the long file
names.  The only way is to look for the candidates using
findfirst/findnext or readdir and fnmatch, and ask the user.  For
example, if you need to delete ALongFileName.Extension, look for
ALONGF~?.EXT.  Note that this is inherently dangerous and unreliable,
so it's probably better to detect this situation and abort telling the
user to boot into Windows 9X.

> How do I know what the short filename equivalents of the long-filenames
> in the manifest will be?

See above.  You can't, not in the general case.

There's a library function _lfn_gen_short_fname that might help, but
it only works when LFNs are enabled.  I could describe the algorithm
used by Windows to generate short aliases, but it's my own gleaning
from what I saw, I have no official place to confirm my experience,
and the specifics depend on the state of NameNumericTail in a tricky
way.

> How do I know if "NameNumericTail" is enabled or disabled?

Create a long file name and look for possible short aliases using the
result of _lfn_gen_short_fname as guidelines.

Note that a possible complication is that the state of NameNumericTail
when the package was unzipped might be different from its state when
the uninstaller runs.

>     The programs runs fine on a machine with long filenames and DJGPP env.
> variable set correctly.  If DJGPP isn't set, it prompts for the directory
> name.

The problem with such programs is that when they backfire, they screw
the user big time.  So IMHO the program should be thoroughly tested on
many different machines, and subject to source-level scrutiny by
several experienced DJGPP programmers (I don't mean myself!) before it
is released.  (Assuming of course that it is indeed better than the
`rm' trick, which I'm not sure it is.)