UUCP Grades
===========

Modern UUCP packages support a priority grade for each command.  The
grades generally range from `A' (the highest) to `Z' followed by `a' to
`z'.  Some UUCP packages (including Taylor UUCP) also support `0' to
`9' before `A'.  Some UUCP packages may permit any ASCII character as a
grade.

On Unix, these grades are encoded in the name of the command file
created by `uucp' or `uux'.  A command file name generally has the form
`C.nnnngssss' where `nnnn' is the remote system name for which the
command is queued, `g' is a single character grade, and `ssss' is a
four character sequence number.  For example, a command file created
for the system `airs' at grade `Z' might be named `C.airsZ2551'.

The remote system name will be truncated to seven characters, to ensure
that the command file name will fit in the 14 character file name limit
of the traditional Unix file system.  UUCP packages which have no other
means of distinguishing which command files are intended for which
systems thus require all systems they connect to to have names that are
unique in the first seven characters.  Some UUCP packages use a variant
of this format which truncates the system name to six characters.  HDB
and Taylor UUCP use a different spool directory format, which allows up
to fourteen characters to be used for each system name.

The sequence number in the command file name may be a decimal integer,
or it may be a hexadecimal integer, or it may contain any alphanumeric
character.  Different UUCP packages are different.

UUPlus Utilities (as FSUUCP, a shareware DOS based UUCP and news
package) uses up to 8 characters for file names in the spool (this is a
DOS file system limitation; actually, with the extension, 11 characters
are available, but FSUUCP reserves that for future use).  FSUUCP
defaults mail to grade `D', and news to grade `N', except that when the
grade of incoming mail can be determined, that grade is preserved if
the mail is forwarded to another system. The default grades may be
changed by editing the `LIB/MAILRC' file for mail, or the `UUPLUS.CFG'
file for news.

UUPC/extended for DOS, OS/2 and Windows NT handles mail at grade `C',
news at grade `d', and file transfers at grade `n'.  The UUPC/extended
`UUCP' and `RMAIL' commands accept grades to override the default, the
others do not.

I do not know how command grades are handled in other non-Unix UUCP
packages.

Modern UUCP packages allow you to restrict file transfer by grade
depending on the time of day.  Typically this is done with a line in
the `Systems' (or `L.sys') file like this:
         airs Any/Z,Any2305-0855 ...
This allows grades `Z' and above to be transferred at any time.  Lower
grades may only be transferred at night.  I believe that this grade
restriction applies to local commands as well as to remote commands,
but I am not sure.  It may only apply if the UUCP package places the
call, not if it is called by the remote system.

Taylor UUCP can use the `timegrade' and `call-timegrade' commands to
achieve the same effect.  It supports the above format when reading
`Systems' or `L.sys'.

UUPC/extended provides the `symmetricgrades' option to announce the
current grade in effect when calling the remote system.

UUPlus allows specification of the highest grade accepted on a per-call
basis with the `-g' option in `UUCICO'.

This sort of grade restriction is most useful if you know what grades
are being used at the remote site.  The default grades used depend on
the UUCP package.  Generally `uucp' and `uux' have different defaults.
A particular grade can be specified with the `-g' option to `uucp' or
`uux'.  For example, to request execution of `rnews' on `airs' with
grade `d', you might use something like
         uux -gd - airs!rnews < article

Uunet queues up mail at grade `C', but increases the grade based on the
size.  News is queued at grade `d', and file transfers at grade `n'.
The example above would allow mail (below some large size) to be
received at any time, but would only permit news to be transferred at
night.