Apparently, though unproven, at 19:34 on Thursday 04 November 2010, James did opine thusly:
> Hello, > > > My google is not sufficient to flesh out the difference > (other than the obvious) of these 2 flags. > > Where would I read about the deep, detailed difference > in flags that appear similar in purpose? $ grep v4l /var/portage/profiles/use.* /var/portage/profiles/use.desc:v4l - Enables video4linux support /var/portage/profiles/use.desc:v4l2 - Enable video4linux2 support To grok that, you need to know a little about the video4linux project. It's safe to assume as step 1 that v4l builds support for video4linux (which is deprecated, moribund, obsolete or discarded depending on your point of view); and v4l2 is support for the currently supported video4linux2 project. Considering your line of work, you likely work with this and already know it. I suppose there are tools that display info about flags (euse is good for the quick one-line description), but if I want to know what is actually being *done* with a USE flag, I look in the ebuild. Nothing quite like reading the code, eh? "equery depends" shows info but it really just greps the portage tree or /var/lib/something with default settings (search installed packages only). Reading the ebuild shows you the context too which often contains very valuable info. "equery hasuse" quickly shows installed packages that use a specified flag. The ffmpeg ebuild shows that ffmpeg supports both projects, you just say which you want. The ebuild for sane-backends reveals: RDEPEND="v4l? ( media-libs/libv4l )" which I'm certain is a current project using v4l2. Oops, initial assumption about flags above is probably wrong. Oh well, it's code, this happens. A lot. > How would/should I know when flags are deprecated, or > on the fast track to becoming deprecated? $PORTDIR/package.mask has info about why things are masked $PORTDIR/use*desc contains the one-line description of flags $PORTDIR/profiles/ChangeLog has useful info about all sorts of stuff. Anything in $PORTDIR with "use" in it's name is worth a look > It there systematic (methologies/syntax) to > discover such nuggets of knowledge? Not that I ever found. It's more a case of familiarity with where things are found and a deep knowledge of grep :-) And ChangeLogs are always the best source of info. That's true for almost all projects out there. -- alan dot mckinnon at gmail dot com
