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Linux Magazine: It's (Not) Magic

Mar 09, 2005, 13:00 (0 Talkback[s])
(Other stories by Jerry Peek)

"While some operating systems use file extensions like .doc,.pdf, and .txt to associate files with applications, Linux systems generally eschews extensions.( Some applications use extensions by convention — C compilers, for instance, expect source filenames to end with .c — but the kernel doesn't enforce this.) Instead, Linux uses a system of magic numbers, where the first few bytes of each executable file tell the kernel how to run it.

"For example, there's no need to name a shell script Plain foo is fine, because Linux figures out the rest( as you'll see in a moment). Magic numbers are widely used on Linux, and not just for executables. Magic numbers are used to identify many other types of files, too..."

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