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NAME

printcap — printer capability data base

SYNOPSIS

DESCRIPTION

The Printcap function is a simplified version of the termcap(5) data base used to describe line printers. The spooling system accesses the printcap file every time it is used, allowing dynamic addition and deletion of printers. Each entry in the data base is used to describe one printer. This data base may not be substituted for, as is possible for termcap(5), because it may allow accounting to be bypassed.

The default printer is normally lp, though the environment variable PRINTER may be used to override this. Each spooling utility supports an option, -P printer, to allow explicit naming of a destination printer.

Refer to the 4.3 BSD Line Printer Spooler Manual for a complete discussion on how to setup the database for a given printer.

CAPABILITIES

Refer to termcap(5) for a description of the file layout.

Each two-letter capability has a human-readable alternate name.

If the local line printer driver supports indentation, the daemon must understand how to invoke it.

FILTERS

The lpd(8) daemon creates a pipeline of filters to process files for various printer types. The filters selected depend on the flags passed to lpr(1). The pipeline set up is:

p	pr | if	regular text + pr(1)
none	if	regular text
c	cf	cifplot
d	df	DVI (tex)
g	gf	plot(3)
n	nf	ditroff
f	rf	Fortran
t	tf	troff
v	vf	raster image

The if filter is invoked with arguments:

The -c flag is passed only if the -l flag (pass control characters literally) is specified to lpr(1). The Width function and length specify the page width and length (from pw and pl respectively) in characters. The -n and -h parameters specify the login name and host name of the owner of the job respectively. The Acct-file function is passed from the af printcap entry.

If no if is specified, of is used instead, with the distinction that of is opened only once, while if is opened for every individual job. Thus, if is better suited to performing accounting. The of is only given the width and length flags.

All other filters are called as:

where width and length are represented in pixels, specified by the px and py entries respectively.

All filters take stdin as the file, stdout as the printer, may log either to stderr or using syslog(3), and must not ignore SIGINT.

REMOTE PRINTING

When printing to a remote printer using rm, it is possible to use either if or of. If both are specified, of is ignored. Both filters behave the same except that they are passed different arguments as above. Specifically, the output filter is terminated and restarted for each file transmitted. This is necessary in order to pass the resulting size to the remote lpd(8).

If the -p flag was passed to lpr(1), pr(1) is not executed locally, but is requested of the remote lpd(8). Any input filtering via if will therefore happen before pr(1) is executed rather than afterwards.

There are some models of network printers which accept jobs from lpd(8), but they ignore the control file for a job and simply print each data file as it arrives at the printer. One side-effect of this behavior is that the printer will ignore any request for multiple copies as given with the -# flag on the lpr(1) command. The rc entry will cause lpd(8) to resend each data file for each copy that the user originally requested. Note that the rc entry should only be specified on hosts which send jobs directly to the printer.

If lp is specified as port@machine (and rm is not in use), printing will be send directly to the given port on the given machine.

TRANSFER STATISTICS

When a print job is transferred to a remote machine (which might be another unix box, or may be a network printer), it may be useful to keep statistics on each transfer. The sr and ss options indicate filenames that lpd should use to store such statistics. A statistics line is written for each datafile of a job as the file is successfully transferred. The format of the line is the same for both the sending and receiving side of a transfer.

Statistics on datafiles being received would be used on a print server, if you are interested in network performance between a variety of machines which are sending jobs to that print server. The print server could collect statistics on the speed of each print job as it arrived on the server.

Statistics on datafiles being sent might be used as a minimal accounting record, when you want to know who sent which jobs to a remote printer, when they were sent, and how large (in bytes) the files were. This will not give include any idea of how many pages were printed, because there is no standard way to get that information back from a remote (network) printer in this case.

LOGGING

Error messages generated by the line printer programs themselves (that is, the lpd(8) and related programs) are logged by syslog(3) using the LOG_LPR facility. Messages printed on stderr of one of the filters are sent to the corresponding lf file. The filters may, of course, use syslogd(8) themselves.

Error messages sent to the console have a carriage return and a line feed appended to them, rather than just a line feed.

SEE ALSO

lpq(1), lpr(1), lprm(1), hosts.lpd(5), termcap(5), chkprintcap(8), lpc(8), lpd(8), pac(8)

4.3 BSD Line Printer Spooler Manual.

HISTORY

The printcap file format appeared in 4.2BSD.