Sidebar: A printcap Entry Dissected

The following is a printcap entry I set up on one of the systems I manage. It shows several features of a normal printcap entry extended with optional filters. This entry is for a Hewlett-Packard LaserJet III connected to a Sun SPARCSTATION 10 using a null modem cable attached to serial port A.

lj|lj3|laser jet 3|:\
:lp=/dev/ttya:br#9600:\
:ms=pass8,opost,ixon,onlcr,crtscts:\
:sd=/var/spool/lpd:\
:lf=/var/adm/lpd-errs:sh:mx#0:\
:if=/usr/local/lib/filters/sethp:\
:cf=/usr/local/lib/filters/setland:\
:df=/usr/local/lib/filters/setnomarg:\
:nf=/usr/local/wp/shbin/wpp:

printcap entries consist of one line of data. Each entry option is separated by a colon. Empty options are allowed, so that :: is okay. When the line is too long, a backslash ("\") extends the entry to the next lines. For more information, see printcap(5).

The sample entries have the following meanings:

lj|lj3|laser jet 3|: The first entry lists names or aliases of the printer, each separated by the vertical bar ("|"). Thus, to use this printer, users may type lj or lj3. One printer in the printcap should have the name lp, representing the system's default printer.

lp=/dev/ttya: This is the physical device the printer is attached to -- in this case, serial port a.

br#9600: This is the baud rate to use for serial communications. Note that a "#" is used between the br option and its value. This convention for numeric options is comparable to the "=" used for string options.

ms=pass8,opost,ixon,onlcr,crtscts: This option holds several communications parameters (see stty(1)).

sd=/var/spool/lpd: This is the spool directory. Files destined for this printer are copied here.

lf=/var/adm/lpd-errs: This is the file to use for logging errors.

sh: This says that the header page should not be printed. This is a boolean option and is not followed by a value. The value is implied by the option's presence.

mx#0: This tells the largest file printable in bytes. Setting mx to 0 removes the size limitation.

if=/usr/local/lib/filters/sethp: This is the input filter to use if no other filter is specified on the command line. sethp initializes the printer, then sends the print job unchanged to the printer.

cf=/usr/local/lib/filters/setland: This is a filter invoked with the -c option on lpr's command line. setland puts the printer in landscape mode before sending the print job.

df=/usr/local/lib/filters/setnomarg: This is another filter, invoked with the -d option. setnomarg sets the margins as close to the edge of the paper as possible and changes to a smaller font.

nf=/usr/local/wp/shbin/wpp: This is a filter installed in printcap by the WordPerfect installation program.

Some printcap entries include fc and fs options. These options clear or set bits to fine-tune the serial communications used by the print system. I try to avoid using them if I can, as they are rather confusing. Information for which bits to set is spread among several man pages and include files (the .h files in the /usr/include directory). The ms option is usually sufficient for what you want to do.