Changing File Permissions

Changing File Permissions

On computer filesystems, different files and directories have permissions that specify who and what can read, write, modify and access them.

Permission Modes

  7       5     5
 user   group  world
 r+w+x  r+x    r+x
 4+2+1  4+0+1  4+0+1  = 755

The permission mode is computed by adding up the following values for the user, the file group, and for everyone else. The diagram shows how.

• Read 4 – Allowed to read files
• Write 2 – Allowed to write/modify files
• eXecute1 – Read/write/delete/modify/directory

  6      4      4
 user   group  world
 r+w    r      r
 4+2+0  4+0+0  4+0+0  = 644

Example Permission Modes