How to set specific permissions for owner and group?

To set specific permissions for the owner and group at the same time, you have two main ways: using Symbolic Notation (letters) or Numeric Notation (numbers).

1. Using Symbolic Notation (Comma Separated)

You can change both the owner (u) and the group (g) in a single command by separating the rules with a comma (no spaces).

Format: chmod u=[perms],g=[perms] filename

• Example: To give the owner rwx (read, write, execute) and the group only rx (read, execute):

  chmod u=rwx,g=rx script.sh

• Example: To add execute to both at once:

  chmod ug+x script.sh

2. Using Numeric Notation (The "Math" Way)

This is often the fastest way to set exactly who has what. You use three digits: the 1st for Owner, 2nd for Group, and 3rd for Others.

Format: chmod [Owner][Group][Others] filename

• Example: Set Owner to rwx (7) and Group to rw- (6), and Others to r-- (4):

  chmod 764 script.sh

  (7 = 4+2+1 | 6 = 4+2 | 4 = 4)

Summary Table for Quick Reference:

Pro Tip: If you want to set the same permissions for both owner and group to be exactly the same, you can use ug:
chmod ug=rw script.sh (This gives both the owner and group read/write access, and removes execute if it was there).