On Mon, Oct 04, 1999 at 12:26:18PM +0100, Edward Betts was heard to say: > Could I clarify some stuff please? > > Are we proposing that all mime-types have binfmt_misc setup? Does that mean, > the kernel will be able to `run' any file in mailcap? Is that what we really > want?
I'm not; I just happened to use the JPEG example in my first mail because I had the magic numbers lying around. On the other hand, you could certainly use them for this. Personally, I don't like the idea: you'll never be able to keep track of every possible file type, and unless you do it'll be way too inconsistent -- eg, file A.jpg works, but A.tiff doesn't (kinda like Windows' associations). Executable stuff should be stuff that's executable.. (although I can see the reasons why being able to do this would be nice) > Another question is are their mime-types for all the programs we might want to > run in this way? The programs I can think of off-hand, are Java, DOS EXE, and > Windows EXE, are there any others? If we go with the ability to run documents > like images and so on, do we have all the mime-types? Are we going to have to > invent new mime-types? Is that a bad thing to do? The other things I was thinking of that we might want to enter were Zcode (Zork and so on) and possibly files for some of the various video game emulators (nestra, snes9x). I think there are mime-types for some of these (isn't Java application/x-java-program? I think DOS EXE may be application/x-msdos-executable or something..). Probably zcode and video game RAMs don't have mime-types (do they even have magic numbers? Hm.) > Some more questions. Is it possible to recognise an html file by a couple of > magic numbers at the beginning? Most html starts <html> or <HTML>, but it is > not certian that it will look like this. Another thought is the possiblilty of > running perl scripts without the bang path, but then how would the shell tell > it is a perl script. 'file' does a pretty good job of that, but it's probably tough to get it right. However, it's worth noting that binfmt_misc can also recognize files based on extension (can you say 'horrible hack'? :) ) > If we put loads of entries into binfmt_misc are we likely to fill some kernel > data table? What happens if it overloads? Do we significantly affect the > performance of the system? If the kernel is checking each file against a list > of magic numbers will it take a long time to run a file? (Probably not the > kernel is fast, and most files we will run will be ELF, which is probably > checked first.) I don't know. I'd imagine it's been tested up to at least 20 or 30 entries.. at any rate, I would've done that if I had written it :) > This is not user independant is it? The system can not be set so that one user > has support for running Java/JPEGs from the command line, and another does > not? Nope. It could be on the Hurd, I think. I'm still trying to get up to speed on the structure there, though.. Daniel -- Exhilaration is that feeling you get just after a great idea hits you, and just before you realize what is wrong with it.
