Linux Permission Calculator

Linux uses a permission system to determine who can read, write, or execute files and directories. These are assigned to three classes: the file owner, the group, and others (public).

The numbers are an octal representation of the permissions. Read=4, Write=2, Execute=1. For example, 7 means Read+Write+Execute (4+2+1), 5 means Read+Execute (4+1). Thus, 755 gives full access to the owner, and read/execute access to group and others.

Numeric notation uses numbers (like 777 or 644) to concisely represent permissions. Symbolic notation uses letters (like rwxr-xr-x) which visually maps directly to read (r), write (w), and execute (x) for each class.

chmod stands for "change mode." It is the standard Linux/Unix terminal command used to change the read, write, and execute permissions of files and directories.

For a directory, "execute" permission means the ability to "enter" the directory (using the cd command) and access its contents. If you remove execute permission, the directory becomes inaccessible.

Permission 777 grants read, write, and execute access to the Owner, the Group, and the Public. It is highly insecure and should almost never be used on production web servers.

The standard permission for typical files (like HTML, CSS, or images on a web server) is 644. This allows the owner to read and write, while everyone else can only read.

The standard permission for directories is 755. This allows the owner to read, write, and enter the directory, while everyone else can only read and enter it.

While chmod changes the *permissions* (who can do what), chown changes the *ownership* (who actually owns the file or group). They are often used together when managing servers.

Yes! macOS is built on a Unix foundation, which means its terminal uses the exact same chmod permissions system and octal numbers as Linux.