# These are special cases.  Don't use them if you're not familiar.
          4000 = Set UID (sticky bit) on execution.
          2000 = Set GUID on execution.

          # Add each one to get the required permission.
          400 = Owner read.
          200 = Owner write.
          100 = Owner execute.
          040 = Group read.
          020 = Group write.
          010 = Group execute.
          004 = World read.
          002 = World write.
          001 = World execute.
          
          # Examples:
          chmod 644 = -rw-r--r--
          chmod 444 = -r--r--r--
          chmod 755 = -rwxr-xr-x
          chmod 700 = -rwx------
          chmod 711 = -rwx--x--x