:set Display options set by user.:set all Display list of all current options, both default and those set by the user.
:set number Display line numbers.
:set showmode Displays in insert mode a message on the prompt
line indicating the type of insert you are making.
:set option Activate option.
:set option= value Assign value to option.
:set option? Display value of option.
:set no option Deactivate option.
:sh Invoke shell.
<Ctrl-d> Return to editor from shell.
! command Execute UNIX command.
:r newfile Read contents of newfile into current file.
:r ! command Read output of UNIX command into current file.