Kali Linux

The file Command – Quickly Identify File Contents in Linux

While file extensions in Linux are optional and often misleading, the file command helps decode what a file truly is. This powerful utility analyzes the actual content, not just the name, and offers a reliable description, vital for system admins, developers, and anyone working with unknown or mixed file types.

What Does file Do?

Examines file headers and content to determine data type.
Provides human-readable descriptions of file format.
Identifies text vs. binary, images, scripts, archives, and more—no guessing from the extension required!

Basic Syntax

file [options] filename

Replace filename with the file to analyze.

Practical Examples

1. Identify File Types

file music_track

Returns “MP3 audio file” (or “ASCII text” if it’s actually just text, regardless of its .mp3 extension).

2. Examine Multiple Files at Once

file *.jpg

Instantly reveals which among your *.jpg files are actual images or just misnamed files.

3. Analyze Files in Subdirectories

file ~/Documents/backup*

Shows what types of backups you actually have (compressed, database dumps, raw text, etc.).

4. Check Scripts or Executables

file install.sh

Output might show “Bourne-Again shell script,” or “ELF 64-bit LSB executable” for compiled binaries.

Important file Command Flags

Option	Function
-b	Hide file name in output
-i	Show MIME type instead of English descriptor
-L	Follow symbolic links
-z	Look inside compressed files

Why Use file?

Critical for verifying downloads or email attachments before opening.
Saves time when working with files missing or using confusing extensions.
Reduces errors in automated workflows and scripts by programmatically confirming file type.