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Gnulpr: An Open Source Project Takes Over LPR Development

Nov 06, 2000, 14:06 (9 Talkback[s])
(Other stories by Nick Moffitt)

[ Thanks to Nick Moffitt for this announcement. ]

Making use of printers is currently the weak point of most POSIX systems (ironic, considering Unix's initial commercial application was typesetting). The Free Software Foundation realized that the GNU system needed a printing subsystem, so they approached Ben Woodard to help fill this gap. A full description of this system and its future development can be found at the gnulpr homepage.

Currently, the standard is LPR. LPR was a quick hack written to meet a DARPA deadline in 1983. It is insufficient for today's printing environment, and development has stalled completely. Some have tried to replace it, with mixed success. We are planning to take over new development of LPR, with the aim of smoothly graduating to a more advanced system.

Gnulpr 1.0 will be the "anthology release". It is a compilation of all of the various pieces that go together to make a proper printing system, including a graphical client and a set of printfilters. This release also includes job status notification, and device-specific feature handling via PPD files.

Gnulpr 1.1 will include the initial steps toward a client library for applications to use in managing print jobs. Future 1.x releases will work toward finishing and completing this library and its interface.

Gnulpr 2.0 will be a radical departure from the architecture currently used by LPR, while retaining a familiar interface for those who need it. While the gnulpr 1.x series is based upon the old BSD lpd spooler, gnulpr 2.x will have a brand new spooler. Gnulpr 2.0 is a much more modular design, focusing on simplicity, security, and flexibility.

The network daemon will be one program, the local job submission daemon will be another, the network transmission filter will be another, etc. Each utility will Do One Thing And Do It Well, and the addition of a new network protocol or spooling policy is merely a matter of implementing a few new utility programs.

Features of the gnulpr 2.x architecture include:

  • A design in accordance with the Software Tools philosophy.
  • A job submission API focused around the familiar (and well-defined) behavior of the file descriptor, with helper functions for applications that do not wish to deal with the details of managing the descriptor.
  • The ability to do away with on-disk spooling, for those who need to keep printer input performance at maximum.
  • The ability to easily install a custom spooling policy, for installations with complicated queueing requirements.
  • Network protocols are handled by standalone client filters, as well as daemons that use the client library to submit print jobs received from remote hosts.
  • Modular data stores for printer enumeration, allowing /etc/printcap, LDAP, or any other data access method to be used.
For a more involved discussion of this architecture, please read the design documents at http://lpr.sourceforge.net/.