Re: [Tracker] Using tracker extractors from other applications

[Martyn Russell <martyn lanedo com>]

On 17/11/10 00:02, Nikolaus Rath wrote:
> Hello,

Hi,

> I would like to use tracker's apparently quite extensive data-extraction
> facilities in my own program. It seems that "tracker-extract -f<file>"
> provides all the functionality that I want, but I am wondering if there
> is a way to avoid having to re-parse output.

The -f command line is a convenience for testing. There is a d-bus API 
you can use which tracker-miner-fs uses, for the spec see:

http://git.gnome.org/browse/tracker/tree/data/dbus/tracker-extract.xml

For examples, see how miner-fs uses it:

http://git.gnome.org/browse/tracker/tree/src/miners/fs/tracker-miner-files.c#n2045

I should add, we use the "Fast" interface, which uses file descriptor 
passing to avoid memory fragmentation and copious copying. There is also 
a non-fast API you can use for testing purposes or if you're not 
intending to send/receive a lot of requests anyway (though we discourage 
it generally if possible).

> Is there a way to talk to tracker-extract via the DBUS API and e.g. tell
> it to return just the nie:plainTextContent attribute? Or some secret,
> undocumented command line option?

You can't ask for just one attribute no, you will have to filter that 
for the moment.

> It would also be nice if there would be a way to process multiple files
> without having to start a new tracker-extract instance for every file.

Using d-bus you shouldn't need to worry about the invocation of 
tracker-extract.

Happy to help,

--
Regards,
Martyn