Recognising Symbolic Links under Windows XP

Recognising Symbolic Links under Windows XP

[davin.pearson]

To Richard Stallman and others...

I have been using Emacs for years and in my opinion it is something of
a religion!

I was recently using Emacs under Gnu/Linux where I learnt about
symbolic links and how useful they are.

These days I am mainly using Emacs under Windows XP so I wondered if
it was possible for Emacs to recognise Windows-style symbolic links
(*.lnk files)

The Cygwin shell and the Windows Explorer recognises *.lnk files so I
thought it would be a good thing if Emacs could be made to recognise
*.lnk files.

After a little bit of C++ and Lisp coding a came up with a solution.
All that you need is a C/C++ program that parses the *.lnk file and
returns via stdout the name of the file/directory that the link points
to.

Suppose that the name of the C/C++ program is d:/bin/lnk.exe.

Then the following snippet of Lisp code achieves the result of taking
you (inside Emacs) to the target of the *.lnk file:

The following code snippet is inside a "cond" form:

     ((string-match "\\.lnk$" filename)
      (shell-command (concat "d:/bin/lnk.exe \"" filename "\""))
      (setq buf (set-buffer "*Shell Command Output*"))
      (goto-char (point-min))
      (setq output (my-find--current-line))
      (cond ((string-match "Usage:" output)
             (message output))
            ((file-exists-p output)
             (find-file output))
            (t
             (message "Cannot find file: %s" output)))
      (kill-buffer buf))

This is all good for my own private purposes but I realise that for my
idea to be included in the standard Gnu Emacs that it must also be
robust.

I have no idea what the format of the *.lnk files is, and a robust
program would have to support all possible examples.

Here is the source code to my lnk.exe file:

> #include "../../2003/noio/io.hh"
>
> int main(int argc, char** argv)
> {
>    const char* usage = "Usage: lnk FILENAME.LNK\n";
>
>    if (argc != 2) {
>       std::cout << usage;
>       exit(EXIT_FAILURE);
>    }
>
>    const char* filename = argv[1];
>    int len = strlen(filename);
>
>    const char* last_four = filename + len - 1 - 4;
>    if (0 == strcmp(last_four, ".lnk")) {
>       std::cout << usage;
>       exit(EXIT_FAILURE);
>    }
>
>    FILE* f  = fopen(filename,"rb");
>
>    string_buffer sb;
>    int ch;
>    while ((ch = fgetc(f)) != -1) {
>       if ((ch >= 0x20) && (ch <= 0x7f)) {
>          sb << (char)ch;
>       }
>    }
>
>    int i = index_of(sb, ":\\") - 1;
>
>    ASSERT(i != -1);
>
>    string link = substring(sb, i, sb.get_length());
>
>    cout << link << '\n';
>
>    exit(EXIT_SUCCESS);
> }
> END_OF_MAIN();
>

Sorry about the usage of my non-standard I/O library, but it would not
be to hard to rewrite this code to use either C or C++ I/O libraries.

Please tell me if you think my idea is a good one!

                                 -*-

P.S. Another idea for making Emacs better would be for dabbrev-expand
to search through the kill ring for possible completions.

Regards,

Davin Pearson      http://www.davinpearson.com

Re: Recognising Symbolic Links under Windows XP

[LENNART BORGMAN]

From: davin.pearson@gmail.com

> To Richard Stallman and others...
> 
> I have been using Emacs for years and in my opinion it is 
> something of
> a religion!
> 
> I was recently using Emacs under Gnu/Linux where I learnt about
> symbolic links and how useful they are.
> 
> These days I am mainly using Emacs under Windows XP so I wondered if
> it was possible for Emacs to recognise Windows-style symbolic links
> (*.lnk files)
> 
> The Cygwin shell and the Windows Explorer recognises *.lnk files 
> so I
> thought it would be a good thing if Emacs could be made to recognise
> *.lnk files.


Did you see WThirtyTwoSymlinks on EmacsWiki:

  http://www.emacswiki.org/cgi-bin/wiki/WThirtyTwoSymlinks

There also a discussion about symlinks here:

  http://lists.trolltech.com/qt-interest/2003-08/thread00550-0.html

Re: Recognising Symbolic Links under Windows XP

[Mathias Dahl]

davin.pearson@gmail.com writes:

> I was recently using Emacs under Gnu/Linux where I learnt about
> symbolic links and how useful they are.
>
> These days I am mainly using Emacs under Windows XP so I wondered if
> it was possible for Emacs to recognise Windows-style symbolic links
> (*.lnk files)

FYI, there is something called "junctions" that NTFS supports. It
works more or less like symbolic links on GNU/Linux or Unix
systems. You need a special command line tool to create them.

You can find one such tool here:

http://www.sysinternals.com/Utilities/Junction.html

I use it to make a symbolic link from my "emacs-22.xyz..." to a folder
with the simpler name "emacs", and it works great.

Re: Recognising Symbolic Links under Windows XP

[davin.pearson]

LENNART BORGMAN wrote:

> Did you see WThirtyTwoSymlinks on EmacsWiki:
>
>   http://www.emacswiki.org/cgi-bin/wiki/WThirtyTwoSymlinks
>
> There also a discussion about symlinks here:
>
>   http://lists.trolltech.com/qt-interest/2003-08/thread00550-0.html

Thanks for you help!  I should have GOOGLED
the subject before sending my post!

Cheers, 

Davin.