Change File Ownership and Permissions

To change the owners of a file, you can use the following commands:

• chown

  • This changes the user who owns a particular file or directory.

• chgrp

  • This changes the group who owns a particular file or directory.

To change the permissions that the owners of a file have, you use the chmod command.

chmod takes two arguments: the permissions to give a file, and the file to change the permissions of. The permissions are represented as a 3-digit number, where each digit represents the permissions to give the user, group, or others, respectively.

Read, write, and execute permissions are represented by the following numbers:

• r - 4

• w - 2

• x - 1

If you want to give someone multiple permissions, you add the numeric representations of those permissions together. For example:

• Read, write, execute (rwx) permissions = (4 + 2 + 1) = 7

• Write, execute (_wx) permissions = (2 + 1) = 3

So let's say you want to give a file the following permissions:

• The user that owns the file should be able to read, write, and execute the file. rwx = (4 + 2 + 1) = 7

• The group that owns the file should be able to read and execute the file. r_x = (4 + 1) = 5

• Anyone else should have no permissions for the file. ___ = 0

The you'd run the following command:

chmod 750 arrayDat.txt

Remembering the syntax for this command can be quite cumbersome, so I recommend using a third-party website such as https://quickref.me/chmod.