What are file permissions in Linux and what does rwx mean?

R, w, and x in Linux file permissions represent read, write and execute permissions respectively. r (read) allows viewing file content or listing directory content; w (write) allows modifying files or adding or deleting files in directory; x (execute) allows running files as programs or entering directories. Permissions are divided into three categories: user (owner), group, and others, and each category can have rwx combinations. Use ls -l to view permissions, the chmod command can modify permissions, and supports symbolic mode and digital mode to set permissions. Common use cases include combinations such as 600, 644, 700, 755, etc. to control access security.

In Linux, file permissions determine who can read, write, or execute a file. Understanding them is key to managing security and access control on your system. The rwx part stands for read, write, and execute — the three basic types of permissions you'll encounter.

What Do r, w, and x Mean?

Each file and directory in Linux has a set of permissions that control access. These are broken down into three categories: user (owner) , group , and others . Each category can have a combination of:

• r (read) – allows viewing the contents of a file or listing the contents of a directory
• w (write) – allows modifying the file or adding/removing files in a directory
• x (execute) – allows running the file as a program or entering a directory

So when you see something like -rwxr-xr-- , it's telling you:

• The owner has full permissions (read, write, execute)
• The group can read and execute
• Others can only read

This is the basic structure and how permissions are displayed in the system.

How to Read Permission Symbols

When you run ls -l , you'll see something like this:

 -rw-r--r-- 1 user group 4096 Apr 5 10:00 filename.txt

The first part ( -rw-r--r-- ) shows the permissions. Breaking it down:

• The first character indicates the file type ( - for regular file, d for directory)
• The next 9 characters are in 3 groups of 3:
  • First 3: user (owner)
  • Second 3: group
  • Third 3: others

Each group shows r, w, and x in that order. If a permission is missing, it shows a - .

So -rw-r--r-- means:

• Owner: read and write
• Group: read only
• Others: read only

How to Change File Permissions with chmod

You can change permissions using the chmod command. There are two common ways to use it:

Symbolic mode

This uses letters and symbols to add, remove, or set permissions:

• adds a permission
• - removes a permission
• = sets it explicitly

Examples:

• chmod ux script.sh – adds execute permission for the user
• chmod go-w file.txt – removes write permission for group and others

Numeric (octal) mode

Each permission has a number:

• r = 4
• w = 2
• x = 1

You add them up for each category:

• 7 (4 2 1) = rwx
• 6 (4 2) = rw-
• 5 (4 1) = rx

So to set a file to -rwxr-xr-- , you'd use:

 chmod 754 filename

This method is faster once you're used to it, especially when setting full permission sets at once.

Common Permission Use Cases

Some permission settings are used frequently:

• 600 (rw------) – Only the owner can read and write (eg, private config files)
• 644 (rw-r--r--) – Owner can edit, others can only read (standard for web files)
• 700 (rwx------) – Only the owner can do anything (private directories)
• 755 (rwxr-xr-x) – Owner has full access, others can run and see contents (common for scripts and public directories)

Be careful with 777 – it gives full access to everyone, which is a big security risk. Don't use it unless you really know what you're doing.

Basically that's it. Permissions in Linux might look confusing at first, but once you break them down into user/group/others and understand what r, w, and x mean, they become much more manageable.

The above is the detailed content of What are file permissions in Linux and what does rwx mean?. For more information, please follow other related articles on the PHP Chinese website!