Specifications

6-12
Guide to Printers and Printing
## Print the banner page
Some applications, when run with certain printers, may require that you turn off page
breaking. If you must turn off page breaking, you can modify the standard interface
program (/usr/lib/lp/model/standard) at this line:
if [ –n ”${FF}” –a ”no” = ”${nofilebreak}” ]
Change the no to yes to turn off page breaking.
5. Specify that the custom interface script print all user–related error messages to the
standard output or to the standard error output. The print service prints standard output
errors on the page and mails standard error to the user.
6. Specify that when printing is complete, the interface script exits with a code advising the
status of the print job. The Exit Codes Table, Exit Codes on page 6-13, describes how
the print service interprets exit codes.
One way of alerting the administrator to a printer fault is to exit with a code of 129.
Unfortunately, if the interface script exits, the print service reprints the print job from the
beginning after the fault is cleared. To get an alert to the administrator without reprinting
the entire job, specify that the interface script send a fault message to the print service,
but wait for the fault to clear. When the fault clears, the interface script resumes printing
the job. When the job finishes printing, the interface script can exit with zero as if the fault
never occurred. An added advantage is that the interface script can detect when the fault
is cleared automatically so that the administrator does not have to re–enable the printer.
To specify that fault messages be sent to the print service, use the lp.tell command. The
standard printer interface code calls the lp.tell command with the LPTELL shell
variable. The lp.tell program sends its standard input to the print service. The print
service forwards the message as an alert to the administrator. If its standard input is
empty, lp.tell does not initiate an alert. Examine the code immediately following these
comments in the standard interface script for an example of how to use the lp.tell
(LPTELL) program:
# Here’s where we set up the $LPTELL program to capture
# fault messages.
#
# Here’s where we print the file.
With the special exit code 129 or lp.tell, the interface script need not disable the printer
itself. Your interface script can disable the printer directly, but doing so overrides the
fault–alerting mechanism. Alerts are sent only if the print service detects that the printer
has faulted, and the special exit code and lp.tell program are its main detection tools.
If the print service must interrupt the printing of a file at any time, it kills the interface
script with a signal 15 (see the signal command and the kill command for more
information).
If the interface script stops upon from receipt of any other signal, the print service
assumes that future print jobs are not affected and continues to use the printer. The print
service notifies the person who submitted the print job that the job did not finish
successfully.
The signals SIGHUP, SIGINT, SIGQUI, and SIGPIP (trap numbers 1, 2, 3, and 13) are
ignored when the interface is invoked. The standard interface script changes this to trap
these signals at appropriate times, interprets these signals to mean that the printer has a
problem, and issues a fault.