Linux handles files differently than Windows or macOS. While file extensions like .txt or .jpg exist, they’re not mandatory for determining file types. Let’s explore how Linux categorizes files and uses extensions.
📁 1. Linux File Types (The Core Seven)
In Linux, every file has a type indicated by the first character in ls -l output:
| Symbol | File Type | Description | Example Command |
|---|---|---|---|
- |
Regular File | Standard files (text, images, binaries) | ls -l file.txt |
d |
Directory | Folder containing other files | ls -ld Documents/ |
l |
Symbolic Link | Shortcut pointing to another file/directory | ln -s target link |
c |
Character Device | Hardware devices (keyboard, serial ports) | ls -l /dev/ttyS0 |
b |
Block Device | Storage devices (hard drives, USB) | ls -l /dev/sda |
p |
Named Pipe | Inter-process communication (FIFO buffers) | mkfifo mypipe |
s |
Socket | Network communication between processes | ss -lnp |
🔤 2. File Extensions in Linux (Convention, Not Requirement)
Unlike Windows, Linux doesn’t rely on extensions to determine file types. Extensions exist primarily for:
- Human readability
- Associating files with applications
- Script organization
Common Extensions:
.sh→ Shell script (chmod +x script.sh).py→ Python script (python3 script.py).gz,.zip,.tar→ Compressed archives.conf→ Configuration files (/etc/*.conf).log→ Log files (/var/log/*.log)
🔍 3. How Linux Identifies File Types
Linux uses magic numbers (file signatures) to detect types:
file document.pdf # Output: "PDF document"
file unknownfile # Checks content regardless of extensionKey Tools:
ls -l→ View file type symbolsfile→ Detect file type by contentstat→ Show detailed file metadata
⚠️ 4. Special Cases to Note
-
Executable Files:
No.exeneeded! Usechmod +x fileto make scripts executable. -
Hidden Files:
Start with.(e.g.,.bashrc). View withls -a. -
Extensionless Files:
Common for binaries (e.g.,/bin/ls) and scripts.
💡 Key Takeaways
- Linux file types are defined by metadata, not extensions.
- Extensions are human-friendly conventions.
- Always use
filewhen unsure about a file’s type. - Permissions matter more than extensions for executability.
> 💻 Try This!
> Run ls -l /dev to see device files, or create a symlink:
> ln -s real_file.txt shortcut_link