[ale] Setting up pseudo-printer

[John Mills]

ALErs -

I have a script to pipe through a decoding filter, and uses 'display' to
show an image on the screen. For example, I can show an image with:
 % cat <encoded_jpeg_file> | /usr/local/bin/viewer_filter

I'm having some trouble setting this up as a printer, so that I could
invoke it with [say]:
 % lpr -P viewer <encoded_jpeg_file>

I'm running RH-7.3. Using the printer configuration tool I defined
'viewer' as a text printer, connected to /dev/null. I then went to
/etc/printcap and made viewer's if=/usr/local/bin/viewer_filter

This doesn't work. Print jobs to 'viewer' just end up as files in 
/var/spool/lpd/viewer/

Any hints on setting this up?

TIA.

 - John Mills
   john.m.mills at alum.mit.edu