From: bradshaw@ccvax.ucd.ie
Newsgroups: comp.protocols.nfs
Subject: SUMMARY. Solution to printer filter problem.
Date: 11 Nov 92 17:19:24 GMT
Organization: University College Dublin


     Following my posting to this (and about 6 other cross posted  newsgroups)
regarding a printer filter problem which I encountered (See posting  >  Title: 
HELP!!! Printer Filter Problem  Date: 3 Nov  1992),  I  received  a  flood  of 
replies, some of which suggested a number of ingenious ideas,  while  an  even 
larger number were requests by other users with similar problems, asking me to 
forward to them any solutions I might come by. To all and sundry who took  the 
time and patience to help, my sincere thanks  for  all  the  replies  to  this 
posting and many others besides....... Instead  of  replying  singly  to  each 
person requesting a report on my progress, I thought it  would  be  easier  to 
post a summary such as this to  the  newsgroups  where  I  first  spawned  the 
problem. Perhaps this could also be  of  use  to  computer-holics  in  general 
...perhaps even part of an FAQ (??!!)......the problems involved  in  reliably 
interfacing printers required to print a variety of document  types  across  a 
network seem to affect users  universally,  while  their  solutions  are  only 
vaguely defined due to the lack of any standard method with which to  approach 
the problems. 
     First of all to recap my original problem.  We  have  just  upgraded  our 
Hewlett Packard Laserjet IIIP to  emulate  postscript  via  the  Pacific  Page 
Emulation Cartridge Ver. 4.31. This  printer  is  mounted  on  a  serial  line 
(/dev/ttya) on our Sun SPARCStation, and is used not only by  the  workstation 
itself, but also a small PC community using PC-NFS V3.5b.  Since  the  printer 
cannot accomodate Postscript and native  HP  PCL  concurrently,  I  sought  to 
enable automatic switching of the printer via an  input  filter,  which,  upon 
determining the  incoming  document  type  (Postscript  or  PCL/other),  would 
download an escape sequence to the printer which would reset  the  printer  to 
the appropriate mode, wait  for  the  reset  to  complete  and  then  continue 
printing the document itself. The escape sequences required  are  provided  in 
the documentation accompanying the cartridge.
     To this end, I acquired a copy of James Clark's "lprps"  software,  which 
comes with an input filter program, "psif", which examines the incoming  print 
file and executes a Bourne shell to enable proper handling  of  that  document 
type. This software is available from many anonymous FTP sites, and comes with 
C source code. In its original form, psif will execute the shell "psif-ps"  if 
the incoming print document is  Postscript,  and  "psif-text"  for  all  other 
types. I therefore set up the  shells  to  not  only  print  the  document  in 
question, but to also download the appropriate escape sequence and "sleep" for 
40 seconds before printing. The  only  problem  I  had  was  that  when  using 
"psif-text" to switch from Postscript to HP PCL, the printer seemed  to  still 
receive data even during the "sleep  40",  after  which  the  following  error 
appeared on the first page of the printout:

%%[ Error: undefined; OffendingCommand: %%
[

     The solution to the problem eventually came from Markus Hirt  and  Ronald 
Florence.....all that was required was to include a '%' at  the  beginning  of 
the escape sequence, so that the sequence is interpreted as a valid Postscript 
command. My  thanks  to  both  Markus  and  Ronald.....the  filter  now  works 
perfectly. Here is the printcap entry I use (If you're  mounting  the  printer 
remotely via PC-NFS use the "raw" filter option in NFSCONF):

# Hewlett Packard LaserJet IIIP

ljet:\
     :lp=/dev/ttya:br#19200:\                # Printer is on serial line ttya
     :sd=/var/spool/lpd:\
     :lf=/var/spool/lpd/log:\
     :rw:sb:sh:sf:\
     :if=/usr/local/lib/psif:\               # Input filter
     :tr=\004:                               # ^D required in postscript
                                             # mode to tell the printer
                                             # when end of job is reached.

If the incoming document is in  postscript  format,  the  shell  "psif-ps"  is 
executed by the input filter program psif:

#!/bin/sh
# psif-ps > A shell to switch printer to postscript if it is  not  already  in 
# postscript mode. The shell checks for the existence of an empty file  called 
# "pcl", which if found means the printer is in native HP PCL mode. An  escape 
# sequence is then sent to the printer to switch the  printer  to  postscript, 
# and the file "pcl" is renamed "postscript", signifying that the  printer  is 
# now in that mode:

if [ -f /var/spool/lpd/printer_mode/pcl ]; then

     mv /var/spool/lpd/printer_mode/pcl /var/spool/lpd/printer_mode/postscript

     echo ["^[&l5257.1058J^M"]     # Send escape sequence to standard output
                                   # i.e. the printer.

     sleep 40                      # Put this shell to "sleep" for 40 seconds
                                   # and wait for reset to complete.

     cat                           # Send standard input (print file) to 
                                   # standard output (printer).

else

     cat                           # If printer is already in postscript mode
                                   # just print document.
fi

If the incoming print file  is  anything  other  than  Postscript,  the  shell 
"psif-text" is executed in a similar manner:

#!/bin/sh
# psif-text > A shell to switch printer to Hp PCL mode if not already in  that 
# mode. Operation is similar to above script, psif-ps.

if [ -f /var/spool/lpd/printer_mode/postscript ]; then

     mv /var/spool/lpd/printer_mode/postscript /var/spool/lpd/printer_mode/pcl

     echo ["%^[&l1057.32259J^M"]   # Send escape sequence....note leading '%'.

     sleep 40                      # Wait for printer to reset.

     cat                           # Print actual print data.

else

     cat                           # Printer already in HP PCL mode. Only need
                                   # to print document..no switching required.
fi

     Note I have used the SunOS echo command. To put an escape character  such 
as Esc (ASCII 27 in decimal)into the echo argument,  use  the  vi  editor  and 
press Ctrl V and then Ctrl [. I hope that the above is of some  use  to  those 
who requested it and perhaps also to those who did  not.  If  anyone  has  any 
questions or problems please feel free to e-mail me at either of the addresses 
below. Once again thanks to one and all for all  the  replies  and  thanks  to 
Markus and Ronald. 'Till we meet again on the news-net.....

                                             Chris Bradshaw

               CBRADH89@IRLEARN.UCD.IE
               BRADSHAW@CCVAX.UCD.IE
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