4x the mini multi-tasking HTTP/1.1 web-server

Configuring the UNIX print-spooler for a Smart Label Printer is quite easy to do (sample scripts are provided with the distribution). The examples below are all designed to provide the following behaviour:

• print-jobs can be submitted with the spooler's normal commands, such as lp or lpr. Users will not be forced to use yet another printer-specific program.
• printer and print-queue status can be queried with the spooler's standard "status" commands, such as lpstat or lpq, on those platforms where such is possible. Users will not be forced to use yet another printer-specific program (Hewlett-Packard, can you hear me?).
• if the printer runs out of labels half-way through a job, the job will wait until new labels are loaded. Whilst waiting for more labels, the print-queue status will (where possible) indicate "printer empty: load labels". As soon as more labels are loaded, the job will continue and the print-queue status will become "ready and printing". The print-job will not be reprinted unnecessarily.
• fatal printing errors (cable pulled out, label jammed in printer, broken printer, command-line errors, garbled communications, printer switched off half way through a job) are handled gracefully: the next print-job is not adversely affected, and the fault is reported. Where possible, a failed print-job will be retried a short while later.
• except where disallowed by local administrative policies, users can select whether an individual print job is accompanied by a one-label banner page or not. All local administrative policies can be applied by the standard spooler mechanisms.

When configuring the print-spooler, there is no need to specify the serial-port baud-rate or other stty/termios settings. slap always hunts for the printers' current baud rate (and switches the printer to its' fastest workable baud rate); and always explicitly sets the stty/termios modes needed to communicate with the printer.

1. create a new "printer-interface" script from the template

   A template SVR4 "printer-interface" script is installed with the rest of the software, as install-dir/lib/slapf.svr4.

   Edit this script, and change the label-size, thus:

   	MEDIA=label-type
   

   The available label-types are listed in the manpage.

   You may also need to change the setting of BAUDMAP: see the comments in the script.

   Save your changes in another file, such as install_dir/lib/queue-name.pi.

2. create the print-queue

   	lpadmin -p queue-name -I simple -T vanilla \
   		-i install-dir/lib/queue-name.pi \
   		-o nobanner -v port
   

   where port is the name of the serial-port device to which the printer is attached, install-dir is the directory where slap was installed, and queue-name is the name of the printer.

   NOTE: you do not need to specify the "-o stty=..." option.

   There are esoteric facilities (custom alerts, printer-classes, etc) that can be specified with other options - see your system documentation, or the manpage for lpadmin.

When submitting print-jobs with lp, you can specify the font to use on the command line, eg:

	lp -d sl1 -o font=thames-bold-italic-24  file1.txt

1. create a new "printer-interface" script from the template

   A template SVR3 "printer-interface" script is installed with the rest of the software, as install-dir/lib/slapf.svr3.

   Edit this script, and change the label-size, thus:

   	MEDIA=label-type
   

   The available label-types are listed in the manpage.

   You may also need to change the setting of BAUDMAP: see the comments in the script.

   Save your changes in another file, such as install_dir/lib/queue-name.pi.

2. create the print-queue

   	lpadmin -p queue-name \
   		-i install-dir/lib/queue-name.pi \
   		-v port
   

   where port is the name of the serial-port device to which the printer is attached, install-dir is the directory where slap was installed, and queue-name is the name of the printer.

When submitting print-jobs with lp, you can specify the font to use on the command line, eg:

	lp -d sl1 -o font=thames-bold-italic-24  file1.txt

Note that the "out-of-labels" printer-status will be reported to the user by mail, rather than being made visible in the output of lpstat. The latter seems to be impossible under the SVR3 spooler.

1. create a new "input-filter" script from the template

   A template shell-script filter is provided as install-dir/lib/slapf.bsd.

   Edit this script, and change the font selection and label-size, thus:

   	FONT=font-name
   	...
   	MEDIA=label-type
   

   The available font-names and label-types are listed in the manpage.

   You may also need to change the setting of BAUDMAP: see the comments in the script.

   Save your changes in another file, such as install_dir/lib/queue-name.if.

2. create the print-queue

   Add the following entry to /etc/printcap:

   queue-name:\
   	:lp=port:rw:\
   	:if=install-dir/lib/queue-name.if:\
   	:sf:sb:sh:sd=spool-directory:
   
   

   where port is the name of the serial-port device to which the printer is attached, install-dir is the directory where slap was installed, and queue-name is the name of the printer. Spool-directory is as described in your local lpd manpage.

   NOTE: you should not need to specify any of the :br:fc:fs:xc:xs: options in the printcap entry.

A common "fix" for this shortcoming is to define several logical printers all pointing to the same physical device, but each defined with a different input filter.

There are several other "fixes" for this LPD design flaw, including using another print-spooler altogether (such as LPRng). See the newsgroups, mailing-lists, et al.

Depending on your version of "lpd", printer errors such as "not responding", "out of labels" or "label jammed" may be reported to the console, to the user's terminal or even via "syslog". You can direct these messages to a specific named file or device by adding an :lf=path: element to the printcap entry for the printer.

Newer releases of LPRng require some additional steps (thanks to Gregory Borzecki for these instructions):

• Change /etc/lpr.config to allow network connections from the print-server to itself (!): uncomment the entry for <@localhost>.
• Change the ownership of the input filter to user daemon, group daemon, and change the permissions to 0600.

LPRng has many more capabilities, thus a more specific method for integrating slap with LPRng would be worth doing.