User interface

The line-printer system consists mainly of the following files and commands:

Figure 1. Printing with the lpr utilities.
Printer daemon that does all the real work.
Program to enter a job in a printer queue.
Spooling queue examination program.
Program to delete jobs from a queue.
Program to administer printers and spooling queues; only root can use this utility.
A master database that describes printers directly attached to a machine and printers accessible across a network. It describes the available printers and how to communicate with them, and it specifies the values for important items (e.g., the spooling directory).