The UNIX system print service is a collection of utilities
that help you, as system administrator (or lp administrator),
to configure, monitor, and control the printers on your system.
See
Figure 4-1, ``Overview of print request processing''.
The print service:
receives files users want to print.
filters the files (if needed) so they can print properly.
schedules the work of one or more printers.
starts programs that interface with the printer(s).
keeps track of the status of jobs.
alerts you to printer problems.
keeps track of mounting forms and filters.
issues error messages when problems arise.
When a user sends a file to a printer,
the print service assigns the request (or ``print job'')
a unique name, the ``request ID''.
The request ID consists of the name of the printer
on which the file is to be printed and a unique number identifying the file.
Use this request ID to find out the
status of the print job or to cancel the print job.
See
``Deleting print jobs''
and
``Viewing jobs in the print queue''.
The print service keeps track of all the print requests in the
request log.
The print job is ``spooled'',
or lined up, with other print jobs to be sent to a printer.
Each print job is processed and waits its turn in line to be printed.
This line of pending print jobs is called a ``print queue''.
Each printer has its own queue;
you can
hold jobs in the queue,
move jobs up in a queue,
or
transfer jobs to another queue.