On Thu, 16 Sep 2010 01:16:20 -0400, Nick Sabalausky <[email protected]> wrote:
"Jonathan M Davis" <[email protected]> wrote in message
news:[email protected]...
On Wednesday, September 15, 2010 12:48:32 Nick Sabalausky wrote:
"Jonathan M Davis" <[email protected]> wrote in message
news:[email protected]...
> If you're on a non-Windows system, the mime-type becomes far more
> important than
> the extension. Most programs in Linux (and I believe MacOS X as well)
> don't care
> about the extension. They just look at the mime type. Extensions
become
> almost
> entirely a thing for the user. So, whether your file is useable
becomes
> more of
> an issue of known mime type than known extension. Still, you don't
> generally
> want to just be making up extensions.
I didn't think unix file systems had a concept of mime type.
They don't have a concept of file extension either. Mime types has to do
with the
contents of the file and file extensions has to do with the name of the
file. It's
programs which interpret those, not the file system. Typically, on
Windows, the
extension is used by the OS to determine which program to use to open a
file. In
unix, it's the mime type that's used to determine that.
The one bit of overlap there is the fact that Windows treats the exe
extension
essentially the way that unix treats the executable file attribute.
Now, I wouldn't advise ditching file extensions in unix, since it not
only
can
help the human using them but there are occasionally programs which
check
the
extension rather the mime type (so, ultimately, you may end up using
both
the
extension and the mime type), but it's primarily the mime type which is
used,
and it's definitely the mime type which is used to determine which
program
to use
to open a file in the desktop environments.
Yea, but my question was more "how in the hell would it know the mime
type
of a file in the first place?" It's obviously not stored in the filename,
and 99.9% is the time it's not stored in the file's data either.
Most binary file formats are designed to be detectable using a "magic
number" that's found at the front of the file. This magic number allows
programs to easily determine the file type.
So yeah, it is stored in the file's data :)
Since then, someone mentioned it typically analyses the content of the
file
and infers the mime type based on that. That's news to me. It would seem
limited and error-prone though, so I have a hard time believing it
doesn't
suppliment that content-analysis with extension-checking in many cases.
I think it's a combination of many things. Try the Linux 'file' command
to see how it detects all different types of files.
-Steve
