A chmod is used to change permission of files and directories.

• form:     chmod  [options]  permissions  filename

permissions

can be represented in two ways.

• Alphabetic combination
• Numeric combination

Alphabetic combination

• User
  • a: All people
  • u: owner
  • g: group
  • o: others
• Permission
  • r: read
  • w: write
  • x: execute
• Example:
  • chmod u=rwx practice.txt : Owner gets all permissions on practice.txt.
  • chmod g-w practice.txt : Group’s write permission on practice.txt is removed.
  • chmod o+rx practice.txt : Others get additional read and execute permissions.
  • chmod a=rwx practice.txt : All people get all permissions.

Numeric Combination

• Permission
  • 4: read
  • 2: write
  • 1: execute
• Example:
  • chmod 755 practice.txt : owner gets all permission. Group and others get read and execute permission.
  • chmod 777 practice.txt : All people get all the permissions.

options