In the case in which the file system
of the server is known or guessed
by the client, the path may possibly
converted into a filename. This
may (in some cases) allow the file
to be retrieved in one RETR command
with no CWD command. In the case
of unix, the filename will in fact
look the same as the URI path. This
must NOT be taken to indicate that
the URL is a unix filename. In
practice, as many FTP servers in
fact have or emulate unix file systems,
it may in fact be time-efficient
to attempt first a direct retrieval
guessing unix syntax, and, if that
fails, to attempt the official sequence
of succession of directory changes
followed by a RETR command.
This may simply things when making
more than one access. When a second
access is required, if no directory
changes have been made, but direct
retrieval has been done, then the
control connection may be kept.
Another possible uninvestigated method
is to use CDUP on the trial assumption
of a hierarchical structure to return
a point in common between the first
and second URLs.
Tim BL