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PLP \- The Public Line Printer Spooler
.br
A Portable UNIX Line Printer Spooler
.br
Release 2.0, 1 June 1988
.AU
Prof. Patrick Powell
.AI
Dept. of Computer Science
University of Minnesota, Minneapolis, Minnesota
.PP
.FS
* UNIX is a trademark of ATT Bell Laboratories.
.FE
.PP
PLP is a reverse engineered version of the Berkeley LPD software.
The functional resemblance between PLP and the
Berkeley Line Printer Spooler (LPD) is intentional;
the source code was written without reference to the
original Berkeley LPD software,
except for some very small sections concerned with networking and the
large characters used for banner printing.
The PLP software has the following features:
.IP 1). 5
The PLP software is intended to be  used in a Networked File System
(NFS) environment,
in which there is a common set of spool queues,
as well as in a loosely coupled environment in which each host
transfers print jobs to a host which has the printer.
.IP 2). 5
Access and permission to use
PLP functions is controlled by entries in a printer permissions file
.I (/usr/spool/lpd/printer_perms.<hostname>)
which can restrict use by user name,
host,
spooler,
page useage,
and a host of other factors.
The printcap file
.I (/usr/spool/lpd/printcap.<hostname>)
is used to specify the printer queues and their operation.
.IP 3). 5
Jobs can now be prioritized.
The maximum priority a user can specify is set in the
printer permissions file.
.IP 4). 5
In addition to the general printer permissions file,
each spool queue can have its own addition printer permissions file.
.IP 5). 5
Line printer control functions can be exercised from a remote host.
Hosts and users with 
.I "remote control permission"
are specified by entries in the printer permissions file.
.IP 6). 5
Unspooling of jobs can be performed by a printcap specified program,
rather than by the PLP unspooler.
This allows PLP to be used as a spooler
and to have spool queues used for various purposes.
.IP 7). 5
Extremely verbose and chatty error messages have been added.
These greatly ease debugging and installation.
In addition,
the
.I checkpc
utility can be used to set file permissions and other items for
use by the PLP software.
.IP 8). 5
The code is quite portable,
with as few system dependencies in it as possible.
It has run on a VAX 4.2, 4.3, and ULTRIX,
SUN 3.0,
and
DG-UX.
