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🗂 Types of Files in Linux

When you run ls -l, the first character of each line indicates the file type:

-rw-r--r--  1 user user  1024 Nov 12 12:00 file.txt
drwxr-xr-x  2 user user  4096 Nov 12 12:00 mydir
lrwxrwxrwx  1 user user    11 Nov 12 12:00 link -> file.txt

Here, -, d, l are file type symbols.

1️⃣ Regular File (-)

  • Symbol: - (dash)
  • Description: Normal file containing text, code, or data.
  • Example: .txt, .jpg, .pdf, .sh
  • Permissions shown after symbol, e.g., -rw-r--r--

2️⃣ Directory (d)

  • Symbol: d

  • Description: Contains other files and directories.

  • Example: /home/user/Documents

  • Permissions apply to directory content: read (r), write (w), execute (x)

    • Execute (x) on a directory means you can enter it with cd.

3️⃣ Symbolic Link (l)

  • Symbol: l
  • Description: Shortcut to another file or directory (like Windows shortcuts).
  • Example: link -> /etc/passwd
  • Can point to files inside or outside the current directory.

4️⃣ Character Device (c)

  • Symbol: c
  • Description: Represents hardware devices that send/receive data one character at a time.
  • Example: /dev/tty0, /dev/zero

5️⃣ Block Device (b)

  • Symbol: b
  • Description: Represents hardware devices that read/write in blocks.
  • Example: /dev/sda, /dev/nvme0n1

6️⃣ FIFO / Named Pipe (p)

  • Symbol: p
  • Description: Pipe used to pass data between processes.
  • Example: mkfifo mypipe
  • Think of it as a “data stream” between programs.

7️⃣ Socket (s)

  • Symbol: s
  • Description: Special file for network communication or inter-process communication (IPC).
  • Example: /var/run/docker.sock
  • Programs use it to send/receive data efficiently.

8️⃣ Sticky Bit (t) and Setuid/Setgid (Special Permissions)

  • Not a file type, but special permission
  • Symbol: t appears on the last execute bit for directories
  • Description: Prevents users from deleting others’ files in a directory.
  • Example: /tmp usually has sticky bit: drwxrwxrwt
  • Setuid (s) → Program runs as owner of the file
  • Setgid (s) → Group ID is inherited when creating files in a directory

✅ Summary Table

Symbol Type Description
- Regular file Text, binary, scripts, etc.
d Directory Contains files/folders
l Symbolic link Shortcut to a file/folder
c Character device Hardware (keyboard, terminal)
b Block device Hardware (hard disk, SSD)
p FIFO / Named Pipe Inter-process communication
s Socket Network/IPC communication
t Sticky bit Restricts deletion in directories
s Setuid/Setgid Special execution permissions

🔹 How to Check File Types

You can use the ls -l command:

ls -l

Or use file command for a more descriptive type:

file /dev/tty0
file /home/user/file.txt

If you want, I can make a visual diagram showing all Linux file types like a flowchart with examples for your GitHub post. It will make it super easy for students to memorize.

Do you want me to do that next?