1. What is Chmod?

Chmod (change mode) is a Linux/Unix command that changes the permissions of files and directories. It uses a numeric (octal) mode or symbolic notation to specify permissions.

2. How Does the Calculator Work?

The calculator uses the chmod mode calculation:

Where:

• User — Owner permissions (first digit)
• Group — Group permissions (second digit)
• Other — All other users (third digit)

Each permission type (read, write, execute) has a numeric value:

• Read (r) = 4
• Write (w) = 2
• Execute (x) = 1

3. Understanding Linux File Permissions

Details: Linux file permissions control who can read, modify, or execute files. The three permission groups (user, group, other) each have three permission types (read, write, execute).

4. Using the Calculator

Tips: Check the boxes for each permission you want to grant. The calculator will compute both the numeric mode and octal representation.

5. Frequently Asked Questions (FAQ)

Q1: What does 755 permission mean?
A: 755 means user has read/write/execute (7), group has read/execute (5), and others have read/execute (5).

Q2: What's the most secure permission for sensitive files?
A: Typically 600 (user read/write, no permissions for group/others) or 700 (user read/write/execute).

Q3: How do I apply these permissions?
A: Use the chmod command: chmod [mode] filename (e.g., chmod 755 script.sh).

Q4: What's the difference between 644 and 755?
A: 644 doesn't include execute permissions for anyone, while 755 includes execute for user/group/others.

Q5: Why use octal notation?
A: Octal notation provides a concise way to represent all permissions with just 3 digits.