User`s guide

3-4
Guide to Printers and Printing
• For print jobs, uses printer and formatting attributes from the database, overridden by any
flags specified on the command line.
• Initializes the printer before processing a print job.
• Provides filters for simple formatting of ASCII documents.
• Uses filters to convert print job data stream to a format supported by the printer.
• Provides support for printing national language characters.
• Passes the filtered data stream of a print job to the printer device driver.
• Generates header and trailer pages for print jobs, if requested.
• Generates multiple copies of print jobs, if requested.
• Reports paper–out, intervention–required, and printer–error conditions.
• Reports problems detected by the filters.
• Cleans up after a job is cancelled.
• For print jobs, provides an environment that you can customize to address specific
printing needs.
You typically do not run printer backend programs directly, although backends such as
compilers can clearly be run directly from the command line. The qdaemon runs the
backend, sending it the names of files and any job control flags that you specify. The
backend communicates with the qdaemon through a status file in the /var/spool/lpd/stat
directory. You can use a queue status query command such as qchk or lpstat to display
status information, including, in the case of a print job, the printer status, the number of
pages printed, and the percentage of the job that is finished.
In AIX, piobe is the standard spooler backend for processing local print jobs.
Formatter Filters
A formatter filter is part of the pipeline created and executed by the default backend for local
printer queues, piobe. A formatter filter provides the capability of either formatting an input
file or passing it through unmodified, based on an input parameter. Even if the formatter
passes the input file unmodified, it still sends printer commands to initialize the printer
before the input file is printed and restores the printer to its original state after printing is
complete.
It is the formatter filter that has the capability of using a virtual printer’s colon file to perform
extensive manipulation of a spooler print job.
Spooler Job
A spooler job is any job that a user submits to the spooler. All job submission commands
must end with the names of one or more files that require processing. You cannot, for
instance, pass a keyword to a backend and have the keyword control the function that
backend will perform; the submitted job must exist in the file system.
The spooler will accept many types of jobs. It is the responsibility of the system
administrator to ensure that the backend for a given queue is capable of processing any job
submitted to that queue.
Printer job types include:
• ASCII
• Postscript
• PCL
• HPGL
• GL