Shell tutorial part 9: changing permissions

In this video we will learn how to change permissions using chmod.
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Video content:
1:03 : chmod |user-groups||+-||permissions| |file-path|. The chmod command changes the permissions of files that we own. The permissions are changed for the given |user-groups|, where 'u' is the owner of the file, 'g' is the owner group, and 'o' are all other users (users who are not the owner and not in the user group). It is possible to add permissions using '+' and to remove permissions using '-', where the permissions are given using their letters: 'r' is the reading permission, 'w' is the writing permission, and 'x' is the execute permission.
Note that chmod can be used with the '-R' flag to recursively change permissions for folders, including all of their contents.
2:04 : chmod go-rwx |file-path|. This command removes all permissions to the given |file-path| from the owner group and all other users, but leaves the owner's permissions untouched.
3:05 : chmod u+r |file-path|. This command adds the reading permission to |file-path|'s owner.
3:34 : chmod XYZ |file-path|. This command changes the permissions to the given |file-path| like so: given a series of 3 numbers XYZ, permissions of the owner are represented by X, the permissions of the owner group by Y, and the permissions of all others by Z where the possible numbers and their corresponding permissions are:
0 : No permissions (---)
1 : Execute permission (--x)
2 : Write permission (-w-)
3 : Execute and write permissions (-wx)
4 : Read permission (r--)
5 : Read and execute permissions (r-x)
6 : Read and write permissions (rw-)
7 : Read, write and execute permissions (rwx)
3:54 : chmod 527 |file-path|. This command sets the permissions of the owner of |file-path| to read and execute (but writing isn't permitted), the permissions of the file's owner group to write only (without read and execute), and gives all permissions to all other users (meaning, they can read, write and execute the given path).
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Relevant links:
Permissions cheatsheet: https://moodle2.cs.huji.ac.il/nu18/mod/page/view.php?id=92559
The complete ownership and permissions playlist: https://www.youtube.com/playlist?list=PLuHmgt1HXB7DU7P3E63apf-zBHtPBqC1A
The complete shell tutorial playlist: https://www.youtube.com/playlist?list=PLuHmgt1HXB7AoJRbiSPzJ22uz34isVF__