Permission types (read, write, execute) in Linux CLI - Commands & Configuration

Introduction

Files and folders on Linux have permissions that control who can read, change, or run them. These permissions help keep your data safe and your system working properly.

When you want to allow someone to open and read a file but not change it

When you need to let a script run as a program

When you want to prevent others from deleting or modifying your files

When setting up shared folders where some users can only view files

When securing sensitive files by restricting access

Commands

This command lists the file details including its permissions so you can see who can read, write, or execute the file.

Terminal

ls -l example.txt

Expected Output

-rw-r--r-- 1 user user 123 Apr 27 12:00 example.txt

→

-l - Shows detailed information including permissions

This command adds execute permission for the file owner so they can run the file as a program or script.

Terminal

chmod u+x example.txt

Expected Output

No output (command runs silently)

→

u+x - Adds execute permission for the user (owner)

Check the permissions again to confirm the execute permission was added for the owner.

Terminal

ls -l example.txt

Expected Output

-rwxr--r-- 1 user user 123 Apr 27 12:00 example.txt

→

-l - Shows detailed information including permissions

This command removes write permission for group and others to prevent them from changing the file.

Terminal

chmod go-w example.txt

Expected Output

No output (command runs silently)

→

go-w - Removes write permission for group and others

Verify the write permission was removed for group and others.

Terminal

ls -l example.txt

Expected Output

-rwxr--r-- 1 user user 123 Apr 27 12:00 example.txt

→

-l - Shows detailed information including permissions

Key Concept

If you remember nothing else from this pattern, remember: read lets you view, write lets you change, and execute lets you run a file.

Common Mistakes

Trying to run a script without execute permission

The system will not allow the file to run and shows a permission denied error

Use chmod u+x filename to add execute permission for the owner before running

Giving write permission to everyone on sensitive files

Anyone can change or delete the file, risking data loss or security issues

Remove write permission for group and others using chmod go-w filename

Confusing permission letters and symbols when using chmod

Incorrect commands may not change permissions as intended or cause errors

Use u (user), g (group), o (others) with + (add), - (remove), = (set exactly) carefully

Summary

Use ls -l to see file permissions and understand who can read, write, or execute a file.

Use chmod with u, g, o and +, -, = to add, remove, or set permissions for user, group, and others.

Remember: read means view, write means change, and execute means run the file.