file

Explanation

The file command is used to determine the file type. Linux does not rely heavily on file extensions to determine what a file is; instead, file examines the contents of a file (looking for "magic numbers") to identify its type (e.g., ASCII text, JPEG image, ELF executable).

Basic Syntax

file [OPTION]... FILE...

Common Flags and Options

Flag	Description
-b, --brief	Do not prepend filenames to output lines.
-i, --mime	Output mime type strings instead of human-readable descriptions.
-L, --dereference	Causes symlinks to be followed.
-z, --uncompress	Try to look inside compressed files.

Real-world Examples

1. Determine the type of a file:

   file image.jpg

2. Check a file without extension:

   file unknown_file

3. Get the MIME type of a file:

   file -i document.pdf