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How can linux know the mimetype of a file? Is there something written inside the file? Does it look at the extension of the file?
Gradient
Posted 2013-05-16T13:04:20.813
Reputation: 531
How does Linux know what is the mimetype of a file?
Answers
5
Through the "magic" bytes in a file. You can do this yourself by running the file command:
file --mime filename
To my understanding, the underlying library is libmagic.
Der Hochstapler
Posted 2013-05-16T13:04:20.813
Reputation: 77 228
3
It does use extensions as well... because things like
– sourcejedi – 2013-05-16T13:38:44.457.txtdon't necessarily have good magic bytes to look for. The exact implementation may depend on which Desktop Environment you mean (e.g. KDE v.s. GNOME). However this is an old freedesktop standard, so the behaviour of most DEs should be very similar.How are magic bytes store in a file in practice? In a text file for example? – Gradient – 2013-05-16T15:04:48.903
@Gradient: There are multiple places. Like
/usr/share/mime/magic, and/usr/share/file/magic.mgc(binary). You can also add your own signatures in/etc/magic. At least these are valid files on my Debian system. – Der Hochstapler – 2013-05-16T15:08:15.5932Plain text files are mainly recognized from the absence of certain bytes that stand for unprintable characters. – chirlu – 2013-05-16T17:31:29.807