printer client/server (lpr/lpd) - a producer-consumer system example
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This directory contains the source code for two programs - tiny-lpr,
that spools files for printing, and tiny-lpd, a printing daemon that takes
files from the spool directory and sends tem to the printer, one file
at a time.

To compile the programs, type 'make' (or 'gmake', to use gnu make).

Experiment with running these programs. Check what happens if you run multiple
'tiny-lpr' (producer) processes at the same time. Check how the system
works if more then one printer daemon (tiny-lpd) is being run at the same time.

Try modifying the system so that only a single printer daemon may be running
at the same time.

Note: to ease running the programs, the spool directoy path is given as
a relative path (this of-course must be changed to a full path in a real
system). Thus, you should run both programs from the source directory in order
for them to work, or modify the file path macro SPOOL_DIR in file
'tiny-lp-common.h' to a full path, and copy the contents of the 'tiny-spooldir'
directory to the new location.

You may also check the semaphore set created by the tiny-lpd program,
by issuing the following command:

ipcs -s

If done after running tiny-lpd, you will see something similar to this:

------ Semaphore Arrays --------
semid     owner     perms     nsems     status      
128       choo      666       2         

note that the 'msgid' field contains a value that is different from what
was supplied to the 'semget()' system call by the tiny-lpd program. This is
the value that you should use when trying to remove the semaphore set,
using the 'ipcrm' command.