(List
  (FunctionDef vbox_version []
    (List
      (Com {[LIT_CHARS cat]} {[DQ [LIT_CHARS /home/ubuntu/.vbox_version]]})
      (Com {[LIT_CHARS return]} {[LIT_CHARS 0]})
    )
  )
  (FunctionDef remove_existing_guest_additions []
    (List
      (Com {[LIT_CHARS service]} {[LIT_CHARS virtualbox-guest-utils]} {[LIT_CHARS stop]})
      (Com {[LIT_CHARS sleep]} {[LIT_CHARS 1]})
      (Com {[LIT_CHARS modprobe]} {[LIT_CHARS -r]} {[LIT_CHARS vboxguest]})
      (Com {[LIT_CHARS apt-get]} {[LIT_CHARS purge]} {[LIT_CHARS -y]} {[LIT_CHARS virtualbox-guest] [LIT_OTHER "*"]})
    )
  )
  (FunctionDef mount_guest_additions []
    (List
      (Com {[LIT_CHARS mkdir]} {[LIT_CHARS /tmp/vbox]})
      (Com {[LIT_CHARS mount]} {[LIT_CHARS -o]} {[LIT_CHARS loop]} {[DQ [LIT_CHARS /home/ubuntu/VBoxGuestAdditions-][ComSub (Com {[LIT_CHARS vbox_version]})][LIT_CHARS .iso]]} {[LIT_CHARS /tmp/vbox]})
    )
  )
  (FunctionDef install_guest_additions []
    (Com {[LIT_CHARS sh]} {[LIT_CHARS /tmp/vbox/VBoxLinuxAdditions.run]})
  )
  (FunctionDef umount_guest_additions []
    (List
      (Com {[LIT_CHARS umount]} {[LIT_CHARS /tmp/vbox]})
      (Com {[LIT_CHARS rmdir]} {[LIT_CHARS /tmp/vbox]})
    )
  )
  (FunctionDef main []
    (List
      (Com {[LIT_CHARS remove_existing_guest_additions]})
      (Com {[LIT_CHARS mount_guest_additions]})
      (Com {[LIT_CHARS install_guest_additions]})
      (Com {[LIT_CHARS umount_guest_additions]})
    )
  )
  (Com {[LIT_CHARS main]})
)