Change to the specified directory. If dir is omitted, $HOME is
assumed.
‘file [mailbox]’
‘fi [mailbox]’
‘folder [mailbox]’
‘fold [mailbox]’
Read in the contents of the specified mailbox. The current mailbox
is updated as if quit command has been issued.
If mailbox is omitted, the command prints the current mailbox
name followed by the summary information regarding it, e.g.: