Re: Fake PDF

[Lee <t.lee.davidson@xxxxxxxxx>]

On 2/24/26 11:11 AM, Gianluigi wrote:
> Il 24/02/26 16:49, Lee ha scritto:
> > Well, I'm not Benoît, but I can tell you that it is not a mistake on your part and that the Mime type IS working.
> >
> > The code of DesktopMime.FromFile() tries first to determine the MIME type by querying the MIME database file (/usr/share/mime/ 
> > globs2) which lists the MIME type based on the file's extension. On my system, line 139 of that file indicates that "*.pdf" 
> > files are of type "application/ pdf".
> >
> > It can be fooled if the extension is not correct. If you need better mime type determination, you can shell out to `file`.
>
> Hi Lee,
>
> I'm probably not understanding what you're trying to say. I tried using BaseName, but I get an error and don't get "File type: 
> Plain Text Document (text/plain)" like I get when opening the same file with Mint's document viewer.
>
> Regards
> Gianluigi

Willy explained what I mean by shelling out to the `file` command. I'd like to explain hopefully a little better about what 
DesktopMime.FromFile() does.

That method queries the system mime type file at "/usr/share/mime/globs2" basically using it as a look-up table. On my system, 
line 139 in that file is "50:application/pdf:*.pdf". So according to that file, all files with a ".pdf" extension are of type 
"application/pdf". It is really stupid as it relies on the file extension as opposed to the file contents.

Simplified, DesktopMime.FromFile() looks up the file extension in "/usr/share/mime/globs2", finds that it is of type 
"application/pdf", and returns that text. BTW, the Stat object created by the Stat() function will also falsely return 
"application/pdf" for that fake PDF file.

The `file` command, on the other hand, will actually look at the header content of the file to determine its actual type.

I hope that helps explain it better.


--
Lee

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