Specifications

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Guide to Printers and Printing
Modifying the mo Virtual Printer Attribute
All virtual printer definitions contain an attribute named mo. The mo attribute specifies the
command string to invoke the device driver interface program. The device driver interface
program is the last process in the input data stream processing pipeline and, in the case of
local spooler queues with piobe as the backend, is usually pioout. It is named the device
driver interface program because, as the last process in the pipeline, it generally opens the
device driver for writing and then writes the processed input data stream to the device
driver. See Datastream Flow for Common Print Jobs on page 3-11 for additional information.
The design of the base operating system spooler allows the root user to replace pieces of
the input data stream processing pipeline with user–written code. In this article an example
of redefining the mo attribute, whose default value is the full path of pioout, to the full path
of a user–written delivery program will be discussed. See Overview of Backend Processing
on page 3-11 for more information.
Handling Unsupported, IP–Addressable Terminal Servers
Suppose that you have an IP–addressable terminal server attached to your Ethernet
network. The terminal server has some number of asynchronous ports to which you can
attach ASCII terminals, modems, printers, or other asynchronous devices. Further suppose
that the terminal server vendor supplied you with a program, named ts_print, that has
the following properties:
• It will read from standard input.
• It accepts a –A flag to specify an IP address.
• It accepts a –P flag to specify a port number.
To turn this into a specific example, suppose that you have an IBM 4029 LaserPrinter that
you want to attach to port 11 on the terminal server and that the terminal server’s IP address
is 9.19.129.101. Your goal is have a queue on a print server to which users can submit
ASCII jobs and have them printed on the 4029 on the terminal server. Though you can use
ts_print from the command line, you would prefer to make use of the formatter filter’s
ability to perform extensive manipulation of both the printer’s mode and the input data
stream. Providing true serial access to the printer is also a goal.
There is more than one way to accomplish this goal. The easiest way involves making a
local ASCII queue on a normal file, instead of on a character–special file in the /dev
directory. After you create the queue and the associated virtual printer, you can modify the
virtual printer to use ts_print.
To begin the queue creation process, enter the SMIT fast path smit mkquedev. A menu
similar to the following displays:
Add a Print Queue
Move cursor to desired item and press Enter. Use arrow keys to scroll.
# ATTACHMENT TYPE DESCRIPTION
local Printer Attached to Local Host
remote Printer Attached to Remote Host
ascii Printer Attached to ASCII Terminal
hpJetDirect Network Printer (HP JetDirect)
file File (in /dev directory)
other User Defined Backend
Choose the file option, then choose a printer type. After you choose the IBM 4029
LaserPrinter (or whatever is correct for your situation), provide the name of an existing file in
the /dev directory. This is the file to which processed jobs submitted to the queue you are
creating are written. The name of the file can be anything that adheres to the base operating