Contributed by &a.kelly;30 September 1995 In order to use printers with FreeBSD, you will need to set them up to work with the Berkeley line printer spooling system, also known as the LPD spooling system. It is the standard printer control system in FreeBSD. This section introduces the LPD spooling system, often simply called LPD. If you are already familiar with LPD or another printer spooling system, you may wish to skip to section Setting up the spooling system. LPD controls everything about a host's printers. It is responsible for a number of things: It controls access to attached printers and printers attached to other hosts on the network. It enables users to submit files to be printed; these submissions are known as jobs. It prevents multiple users from accessing a printer at the same time by maintaining a queue for each printer. It can print header pages (also known as banner or burst pages) so users can easily find jobs they have printed in a stack of printouts. It takes care of communications parameters for printers connected on serial ports. It can send jobs over the network to another LPD spooler on another host. It can run special filters to format jobs to be printed for various printer languages or printer capabilities. It can account for printer usage. Through a configuration file, and by providing the special filter programs, you can enable the LPD system to do all or some subset of the above for a great variety of printer hardware. If you are the sole user of your system, you may be wondering why you should bother with the spooler when you do not need access control, header pages, or printer accounting. While it is possible to enable direct access to a printer, you should use the spooler anyway since LPD prints jobs in the background; you do not have to wait for data to be copied to the printer. LPD can conveniently run a job to be printed through filters to add date/time headers or convert a special file format (such as a TeX DVI file) into a format the printer will understand. You will not have to do these steps manually. Many free and commercial programs that provide a print feature usually expect to talk to the spooler on your system. By setting up the spooling system, you will more easily support other software you may later add or already have. To use printers with the LPD spooling system, you will need to set up both your printer hardware and the LPD software. This document describes two levels of setup: See section Simple Printer Setup to learn how to connect a printer, tell LPD how to communicate with it, and print plain text files to the printer. See section Advanced Printer Setup to find out how to print a variety of special file formats, to print header pages, to print across a network, to control access to printers, and to do printer accounting. This section tells how to configure printer hardware and the LPD software to use the printer. It teaches the basics: Section Hardware Setup gives some hints on connecting the printer to a port on your computer. Section Software Setup shows how to setup the LPD spooler configuration file /etc/printcap. If you are setting up a printer that uses a network protocol to accept data to print instead of a serial or parallel interface, see Printers With Networked Data Stream Interaces. Although this section is called “Simple Printer Setup,” it is actually fairly complex. Getting the printer to work with your computer and the LPD spooler is the hardest part. The advanced options like header pages and accounting are fairly easy once you get the printer working. This section tells about the various ways you can connect a printer to your PC. It talks about the kinds of ports and cables, and also the kernel configuration you may need to enable FreeBSD to speak to the printer. If you have already connected your printer and have successfully printed with it under another operating system, you can probably skip to section Software Setup. Nearly all printers you can get for a PC today support one or both of the following interfaces: Serial interfaces use a serial port on your computer to send data to the printer. Serial interfaces are common in the computer industry and cables are readily available and also easy to construct. Serial interfaces sometimes need special cables and might require you to configure somewhat complex communications options. Parallel interfaces use a parallel port on your computer to send data to the printer. Parallel interfaces are common in the PC market. Cables are readily available but more difficult to construct by hand. There are usually no communications options with parallel interfaces, making their configuration exceedingly simple. Parallel interfaces are sometimes known as “Centronics” interfaces, named after the connector type on the printer. In general, serial interfaces are slower than parallel interfaces. Parallel interfaces usually offer just one-way communication (computer to printer) while serial gives you two-way. Many newer parallel ports can also receive data from the printer, but only few printers need to send data back to the computer. And FreeBSD does not support two-way parallel communication yet. Usually, the only time you need two-way communication with the printer is if the printer speaks PostScript. PostScript printers can be very verbose. In fact, PostScript jobs are actually programs sent to the printer; they need not produce paper at all and may return results directly to the computer. PostScript also uses two-way communication to tell the computer about problems, such as errors in the PostScript program or paper jams. Your users may be appreciative of such information. Furthermore, the best way to do effective accounting with a PostScript printer requires two-way communication: you ask the printer for its page count (how many pages it has printed in its lifetime), then send the user's job, then ask again for its page count. Subtract the two values and you know how much paper to charge the user. So, which interface should you use? If you need two-way communication, use a serial port. FreeBSD does not yet support two-way communication over a parallel port. If you do not need two-way communication and can pick parallel or serial, prefer the parallel interface. It keeps a serial port free for other peripherals—such as a terminal or a modem—and is faster most of the time. It is also easier to configure. Finally, use whatever works. To hook up a printer using a parallel interface, connect the Centronics cable between the printer and the computer. The instructions that came with the printer, the computer, or both should give you complete guidance. Remember which parallel port you used on the computer. The first parallel port is /dev/lpt0 to FreeBSD; the second is /dev/lpt1, and so on. To hook up a printer using a serial interface, connect the proper serial cable between the printer and the computer. The instructions that came with the printer, the computer, or both should give you complete guidance. If you are unsure what the “proper serial cable” is, you may wish to try one of the following alternatives: A modem cable connects each pin of the connector on one end of the cable straight through to its corresponding pin of the connector on the other end. This type of cable is also known as a “DTE-to-DCE” cable. A null-modem cable connects some pins straight through, swaps others (send data to receive data, for example), and shorts some internally in each connector hood. This type of cable is also known as a “DTE-to-DTE” cable. A serial printer cable, required for some unusual printers, is like the null modem cable, but sends some signals to their counterparts instead of being internally shorted. You should also set up the communications parameters for the printer, usually through front-panel controls or DIP switches on the printer. Choose the highest bps (bits per second, sometimes baud rate) rate that both your computer and the printer can support. Choose 7 or 8 data bits; none, even, or odd parity; and 1 or 2 stop bits. Also choose a flow control protocol: either none, or XON/XOFF (also known as “in-band” or “software”) flow control. Remember these settings for the software configuration that follows. This section describes the software setup necessary to print with the LPD spooling system in FreeBSD. Here is an outline of the steps involved: Configure your kernel, if necessary, for the port you are using for the printer; section Kernel Configuration tells you what you need to do. Set the communications mode for the parallel port, if you are using a parallel port; section Setting the Communication Mode for the Parallel Port gives details. Test if the operating system can send data to the printer. Section Checking Printer Communications gives some suggestions on how to do this. Set up LPD for the printer by modifying the file /etc/printcap. Section The /etc/printcap File shows you how. The operating system kernel is compiled to work with a specific set of devices. The serial or parallel interface for your printer is a part of that set. Therefore, it might be necessary to add support for an additional serial or parallel port if your kernel is not already configured for one. To find out if the kernel you are currently using supports a serial interface, type: &prompt.root; dmesg | grep sioN Where N is the number of the serial port, starting from zero. If you see output similar to the following: sio2 at 0x3e8-0x3ef irq 5 on isa sio2: type 16550A then the kernel supports the port. To find out if the kernel supports a parallel interface, type: &prompt.root; dmesg | grep lptN Where N is the number of the parallel port, starting from zero. If you see output similar to the following lpt0 at 0x378-0x37f on isa then the kernel supports the port. You might have to reconfigure your kernel in order for the operating system to recognize and use the parallel or serial port you are using for the printer. To add support for a serial port, see the section on kernel configuration. To add support for a parallel port, see that section and the section that follows. Even though the kernel may support communication along a serial or parallel port, you will still need a software interface through which programs running on the system can send and receive data. That is what entries in the /dev directory are for. To add a /dev entry for a port: Become root with the su command. Enter the root password when prompted. Change to the /dev directory: &prompt.root; cd /dev Type: &prompt.root; ./MAKEDEV port Where port is the device entry for the port you want to make. Use lpt0 for the first parallel port, lpt1 for the second, and so on; use ttyd0 for the first serial port, ttyd1 for the second, and so on. Type: &prompt.root; ls -l port to make sure the device entry got created. When you are using the parallel interface, you can choose whether FreeBSD should use interrupt-driven or polled communication with the printer. The interrupt-driven method is the default with the GENERIC kernel. With this method, the operating system uses an IRQ line to determine when the printer is ready for data. The polled method directs the operating system to repeatedly ask the printer if it is ready for more data. When it responds ready, the kernel sends more data. The interrupt-driven method is somewhat faster but uses up a precious IRQ line. You should use whichever one works. You can set the communications mode in two ways: by configuring the kernel or by using the lptcontrol program. To set the communications mode by configuring the kernel: Edit your kernel configuration file. Look for or add an lpt0 entry. If you are setting up the second parallel port, use lpt1 instead. Use lpt2 for the third port, and so on. If you want interrupt-driven mode, add the irq specifier: device lpt0 at isa? port? tty irq N vector lptintr Where N is the IRQ number for your computer's parallel port. If you want polled mode, do not add the irq specifier: device lpt0 at isa? port? tty vector lptintr Save the file. Then configure, build, and install the kernel, then reboot. See kernel configuration for more details. To set the communications mode with lptcontrol: Type: &prompt.root; lptcontrol -i -u N to set interrupt-driven mode for lptN. Type: &prompt.root; lptcontrol -p -u N to set polled-mode for lptN. You could put these commands in your /etc/rc.local file to set the mode each time your system boots. See lptcontrol8 for more information. Before proceeding to configure the spooling system, you should make sure the operating system can successfully send data to your printer. It is a lot easier to debug printer communication and the spooling system separately. To test the printer, we will send some text to it. For printers that can immediately print characters sent to them, the program lptest is perfect: it generates all 96 printable ASCII characters in 96 lines. For a PostScript (or other language-based) printer, we will need a more sophisticated test. A small PostScript program, such as the following, will suffice: %!PS 100 100 moveto 300 300 lineto stroke 310 310 moveto /Helvetica findfont 12 scalefont setfont (Is this thing working?) show showpage When this document refers to a printer language, I am assuming a language like PostScript, and not Hewlett Packard's PCL. Although PCL has great functionality, you can intermingle plain text with its escape sequences. PostScript cannot directly print plain text, and that is the kind of printer language for which we must make special accommodations. This section tells you how to check if FreeBSD can communicate with a printer connected to a parallel port. To test a printer on a parallel port: Become root with su. Send data to the printer. If the printer can print plain text, then use lptest. Type: &prompt.root; lptest > /dev/lptN Where N is the number of the parallel port, starting from zero. If the printer understands PostScript or other printer language, then send a small program to the printer. Type: &prompt.root; cat > /dev/lptN Then, line by line, type the program carefully as you cannot edit a line once you have pressed RETURN or ENTER. When you have finished entering the program, press CONTROL+D, or whatever your end of file key is. Alternatively, you can put the program in a file and type: &prompt.root; cat file > /dev/lptN Where file is the name of the file containing the program you want to send to the printer. You should see something print. Do not worry if the text does not look right; we will fix such things later. This section tells you how to check if FreeBSD can communicate with a printer on a serial port. To test a printer on a serial port: Become root with su. Edit the file /etc/remote. Add the following entry: printer:dv=/dev/port:br#bps-rate:pa=parity Where port is the device entry for the serial port (ttyd0, ttyd1, etc.), bps-rate is the bits-per-second rate at which the printer communicates, and parity is the parity required by the printer (either even, odd, none, or zero). Here is a sample entry for a printer connected via a serial line to the third serial port at 19200 bps with no parity: printer:dv=/dev/ttyd2:br#19200:pa=none Connect to the printer with tip. Type: &prompt.root; tip printer If this step does not work, edit the file /etc/remote again and try using /dev/cuaaN instead of /dev/ttydN. Send data to the printer. If the printer can print plain text, then use lptest. Type: ~$lptest If the printer understands PostScript or other printer language, then send a small program to the printer. Type the program, line by line, very carefully as backspacing or other editing keys may be significant to the printer. You may also need to type a special end-of-file key for the printer so it knows it received the whole program. For PostScript printers, press CONTROL+D. Alternatively, you can put the program in a file and type: ~>file Where file is the name of the file containing the program. After tip sends the file, press any required end-of-file key. You should see something print. Do not worry if the text does not look right; we will fix that later. At this point, your printer should be hooked up, your kernel configured to communicate with it (if necessary), and you have been able to send some simple data to the printer. Now, we are ready to configure LPD to control access to your printer. You configure LPD by editing the file /etc/printcap. The LPD spooling system reads this file each time the spooler is used, so updates to the file take immediate effect. The format of the printcap file is straightforward. Use your favorite text editor to make changes to /etc/printcap. The format is identical to other capability files like /usr/share/misc/termcap and /etc/remote. For complete information about the format, see the cgetent3. The simple spooler configuration consists of the following steps: Pick a name (and a few convenient aliases) for the printer, and put them in the /etc/printcap file; see Naming the Printer. Turn off header pages (which are on by default) by inserting the sh capability; see Suppressing Header Pages. Make a spooling directory, and specify its location with the sd capability; see Making the Spooling Directory. Set the /dev entry to use for the printer, and note it in /etc/printcap with the lp capability; see Identifying the Printer Device. Also, if the printer is on a serial port, set up the communication parameters with the fs, fc, xs, and xc capabilities; see Configuring Spooler Communications Parameters. Install a plain text input filter; see Installing the Text Filter Test the setup by printing something with the lpr command; see Trying It Out and Troubleshooting. Language-based printers, such as PostScript printers, cannot directly print plain text. The simple setup outlined above and described in the following sections assumes that if you are installing such a printer you will print only files that the printer can understand. Users often expect that they can print plain text to any of the printers installed on your system. Programs that interface to LPD to do their printing usually make the same assumption. If you are installing such a printer and want to be able to print jobs in the printer language and print plain text jobs, you are strongly urged to add an additional step to the simple setup outlined above: install an automatic plain-text-to-PostScript (or other printer language) conversion program. Section Accommodating Plain Text Jobs on PostScript Printers tells how to do this. The first (easy) step is to pick a name for your printer. It really does not matter whether you choose functional or whimsical names since you can also provide a number aliases for the printer. At least one of the printers specified in the /etc/printcap should have the alias lp. This is the default printer's name. If users do not have the PRINTER environment variable nor specify a printer name on the command line of any of the LPD commands, then lp will be the default printer they get to use. Also, it is common practice to make the last alias for a printer be a full description of the printer, including make and model. Once you have picked a name and some common aliases, put them in the /etc/printcap file. The name of the printer should start in the leftmost column. Separate each alias with a vertical bar and put a colon after the last alias. In the following example, we start with a skeletal /etc/printcap that defines two printers (a Diablo 630 line printer and a Panasonic KX-P4455 PostScript laser printer): # # /etc/printcap for host rose # rattan|line|diablo|lp|Diablo 630 Line Printer: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4: In this example, the first printer is named rattan and has as aliases line, diablo, lp, and Diablo 630 Line Printer. Since it has the alias lp, it is also the default printer. The second is named bamboo, and has as aliases ps, PS, S, panasonic, and Panasonic KX-P4455 PostScript v51.4. The LPD spooling system will by default print a header page for each job. The header page contains the user name who requested the job, the host from which the job came, and the name of the job, in nice large letters. Unfortunately, all this extra text gets in the way of debugging the simple printer setup, so we will suppress header pages. To suppress header pages, add the sh capability to the entry for the printer in /etc/printcap. Here is the example /etc/printcap with sh added: # # /etc/printcap for host rose - no header pages anywhere # rattan|line|diablo|lp|Diablo 630 Line Printer:\ :sh: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh: Note how we used the correct format: the first line starts in the leftmost column, and subsequent lines are indented with a single TAB. Every line in an entry except the last ends in a backslash character. The next step in the simple spooler setup is to make a spooling directory, a directory where print jobs reside until they are printed, and where a number of other spooler support files live. Because of the variable nature of spooling directories, it is customary to put these directories under /var/spool. It is not necessary to backup the contents of spooling directories, either. Recreating them is as simple as running mkdir. It is also customary to make the directory with a name that is identical to the name of the printer, as shown below: &prompt.root; mkdir /var/spool/printer-name However, if you have a lot of printers on your network, you might want to put the spooling directories under a single directory that you reserve just for printing with LPD. We will do this for our two example printers rattan and bamboo: &prompt.root; mkdir /var/spool/lpd &prompt.root; mkdir /var/spool/lpd/rattan &prompt.root; mkdir /var/spool/lpd/bamboo If you are concerned about the privacy of jobs that users print, you might want to protect the spooling directory so it is not publicly accessible. Spooling directories should be owned and be readable, writable, and searchable by user daemon and group daemon, and no one else. We will do this for our example printers: &prompt.root; chown daemon.daemon /var/spool/lpd/rattan &prompt.root; chown daemon.daemon /var/spool/lpd/bamboo &prompt.root; chmod 770 /var/spool/lpd/rattan &prompt.root; chmod 770 /var/spool/lpd/bamboo Finally, you need to tell LPD about these directories using the /etc/printcap file. You specify the pathname of the spooling directory with the sd capability: # # /etc/printcap for host rose - added spooling directories # rattan|line|diablo|lp|Diablo 630 Line Printer:\ :sh:sd=/var/spool/lpd/rattan: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh:sd=/var/spool/lpd/bamboo: Note that the name of the printer starts in the first column but all other entries describing the printer should be indented with a tab and each line escaped with a backslash. If you do not specify a spooling directory with sd, the spooling system will use /var/spool/lpd as a default. In section Adding /dev Entries for the Ports, we identified which entry in the /dev directory FreeBSD will use to communicate with the printer. Now, we tell LPD that information. When the spooling system has a job to print, it will open the specified device on behalf of the filter program (which is responsible for passing data to the printer). List the /dev entry pathname in the /etc/printcap file using the lp capability. In our running example, let us assume that rattan is on the first parallel port, and bamboo is on a sixth serial port; here are the additions to /etc/printcap: # # /etc/printcap for host rose - identified what devices to use # rattan|line|diablo|lp|Diablo 630 Line Printer:\ :sh:sd=/var/spool/lpd/rattan:\ :lp=/dev/lpt0: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh:sd=/var/spool/lpd/bamboo:\ :lp=/dev/ttyd5: If you do not specify the lp capability for a printer in your /etc/printcap file, LPD uses /dev/lp as a default. /dev/lp currently does not exist in FreeBSD. If the printer you are installing is connected to a parallel port, skip to the section Installing the Text Filter. Otherwise, be sure to follow the instructions in the next section. For printers on serial ports, LPD can set up the bps rate, parity, and other serial communication parameters on behalf of the filter program that sends data to the printer. This is advantageous since: It lets you try different communication parameters by simply editing the /etc/printcap file; you do not have to recompile the filter program. It enables the spooling system to use the same filter program for multiple printers which may have different serial communication settings. The following /etc/printcap capabilities control serial communication parameters of the device listed in the lp capability: br#bps-rate Sets the communications speed of the device to bps-rate, where bps-rate can be 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, or 38400 bits-per-second. fc#clear-bits Clears the flag bits clear-bits in the sgttyb structure after opening the device. fs#set-bits Sets the flag bits set-bits in the sgttyb structure. xc#clear-bits Clears local mode bits clear-bits after opening the device. xs#set-bits Sets local mode bits set-bits. For more information on the bits for the fc, fs, xc, and xs capabilities, see the file /usr/include/sys/ioctl_compat.h. When LPD opens the device specified by the lp capability, it reads the flag bits in the sgttyb structure; it clears any bits in the fc capability, then sets bits in the fs capability, then applies the resultant setting. It does the same for the local mode bits as well. Let us add to our example printer on the sixth serial port. We will set the bps rate to 38400. For the flag bits, we will set the TANDEM, ANYP, LITOUT, FLUSHO, and PASS8 flags. For the local mode bits, we will set the LITOUT and PASS8 flags: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh:sd=/var/spool/lpd/bamboo:\ :lp=/dev/ttyd5:fs#0x82000c1:xs#0x820: We are now ready to tell LPD what text filter to use to send jobs to the printer. A text filter, also known as an input filter, is a program that LPD runs when it has a job to print. When LPD runs the text filter for a printer, it sets the filter's standard input to the job to print, and its standard output to the printer device specified with the lp capability. The filter is expected to read the job from standard input, perform any necessary translation for the printer, and write the results to standard output, which will get printed. For more information on the text filter, see section Filters. For our simple printer setup, the text filter can be a small shell script that just executes /bin/cat to send the job to the printer. FreeBSD comes with another filter called lpf that handles backspacing and underlining for printers that might not deal with such character streams well. And, of course, you can use any other filter program you want. The filter lpf is described in detail in section lpf: a Text Filter. First, let us make the shell script /usr/local/libexec/if-simple be a simple text filter. Put the following text into that file with your favorite text editor: #!/bin/sh # # if-simple - Simple text input filter for lpd # Installed in /usr/local/libexec/if-simple # # Simply copies stdin to stdout. Ignores all filter arguments. /bin/cat && exit 0 exit 2 Make the file executable: &prompt.root; chmod 555 /usr/local/libexec/if-simple And then tell LPD to use it by specifying it with the if capability in /etc/printcap. We will add it to the two printers we have so far in the example /etc/printcap: # # /etc/printcap for host rose - added text filter # rattan|line|diablo|lp|Diablo 630 Line Printer:\ :sh:sd=/var/spool/lpd/rattan:\ :lp=/dev/lpt0:\ :if=/usr/local/libexec/if-simple: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh:sd=/var/spool/lpd/bamboo:\ :lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:\ :if=/usr/local/libexec/if-simple: You have reached the end of the simple LPD setup. Unfortunately, congratulations are not quite yet in order, since we still have to test the setup and correct any problems. To test the setup, try printing something. To print with the LPD system, you use the command lpr, which submits a job for printing. You can combine lpr with the lptest program, introduced in section Checking Printer Communications to generate some test text. To test the simple LPD setup: Type: &prompt.root; lptest 20 5 | lpr -Pprinter-name Where printer-name is a the name of a printer (or an alias) specified in /etc/printcap. To test the default printer, type lpr without any -P argument. Again, if you are testing a printer that expects PostScript, send a PostScript program in that language instead of using lptest. You can do so by putting the program in a file and typing lpr file. For a PostScript printer, you should get the results of the program. If you are using lptest, then your results should look like the following: !"#$%&'()*+,-./01234 "#$%&'()*+,-./012345 #$%&'()*+,-./0123456 $%&'()*+,-./01234567 %&'()*+,-./012345678 To further test the printer, try downloading larger programs (for language-based printers) or running lptest with different arguments. For example, lptest 80 60 will produce 60 lines of 80 characters each. If the printer did not work, see the next section, Troubleshooting. After performing the simple test with lptest, you might have gotten one of the following results instead of the correct printout: It worked, after awhile; or, it did not eject a full sheet. The printer printed the above, but it sat for awhile and did nothing. In fact, you might have needed to press a PRINT REMAINING or FORM FEED button on the printer to get any results to appear. If this is the case, the printer was probably waiting to see if there was any more data for your job before it printed anything. To fix this problem, you can have the text filter send a FORM FEED character (or whatever is necessary) to the printer. This is usually sufficient to have the printer immediately print any text remaining in its internal buffer. It is also useful to make sure each print job ends on a full sheet, so the next job does not start somewhere on the middle of the last page of the previous job. The following replacement for the shell script /usr/local/libexec/if-simple prints a form feed after it sends the job to the printer: #!/bin/sh # # if-simple - Simple text input filter for lpd # Installed in /usr/local/libexec/if-simple # # Simply copies stdin to stdout. Ignores all filter arguments. # Writes a form feed character (\f) after printing job. /bin/cat && printf "\f" && exit 0 exit 2 It produced the “staircase effect.” You got the following on paper: !"#$%&'()*+,-./01234 "#$%&'()*+,-./012345 #$%&'()*+,-./0123456 You have become another victim of the staircase effect, caused by conflicting interpretations of what characters should indicate a new-line. UNIX-style operating systems use a single character: ASCII code 10, the line feed (LF). MS-DOS, OS/2, and others uses a pair of characters, ASCII code 10 and ASCII code 13 (the carriage return or CR). Many printers use the MS-DOS convention for representing new-lines. When you print with FreeBSD, your text used just the line feed character. The printer, upon seeing a line feed character, advanced the paper one line, but maintained the same horizontal position on the page for the next character to print. That is what the carriage return is for: to move the location of the next character to print to the left edge of the paper. Here is what FreeBSD wants your printer to do: Printer received CR Printer prints CR Printer received LF Printer prints CR + LF Here are some ways to achieve this: Use the printer's configuration switches or control panel to alter its interpretation of these characters. Check your printer's manual to find out how to do this. If you boot your system into other operating systems besides FreeBSD, you may have to reconfigure the printer to use a an interpretation for CR and LF characters that those other operating systems use. You might prefer one of the other solutions, below. Have FreeBSD's serial line driver automatically convert LF to CR+LF. Of course, this works with printers on serial ports only. To enable this feature, set the CRMOD bit in fs capability in the /etc/printcap file for the printer. Send an escape code to the printer to have it temporarily treat LF characters differently. Consult your printer's manual for escape codes that your printer might support. When you find the proper escape code, modify the text filter to send the code first, then send the print job. Here is an example text filter for printers that understand the Hewlett-Packard PCL escape codes. This filter makes the printer treat LF characters as a LF and CR; then it sends the job; then it sends a form feed to eject the last page of the job. It should work with nearly all Hewlett Packard printers. #!/bin/sh # # hpif - Simple text input filter for lpd for HP-PCL based printers # Installed in /usr/local/libexec/hpif # # Simply copies stdin to stdout. Ignores all filter arguments. # Tells printer to treat LF as CR+LF. Writes a form feed character # after printing job. printf "\033&k2G" && cat && printf "\033&l0H" && exit 0 exit 2 Here is an example /etc/printcap from a host called orchid. It has a single printer attached to its first parallel port, a Hewlett Packard LaserJet 3Si named teak. It is using the above script as its text filter: # # /etc/printcap for host orchid # teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\ :lp=/dev/lpt0:sh:sd=/var/spool/lpd/teak:mx#0:\ :if=/usr/local/libexec/hpif: It overprinted each line. The printer never advanced a line. All of the lines of text were printed on top of each other on one line. This problem is the “opposite” of the staircase effect, described above, and is much rarer. Somewhere, the LF characters that FreeBSD uses to end a line are being treated as CR characters to return the print location to the left edge of the paper, but not also down a line. Use the printer's configuration switches or control panel to enforce the following interpretation of LF and CR characters: Printer receives Printer prints CR CR LF CR + LF The printer lost characters. While printing, the printer did not print a few characters in each line. The problem might have gotten worse as the printer ran, losing more and more characters. The problem is that the printer cannot keep up with the speed at which the computer sends data over a serial line. (This problem should not occur with printers on parallel ports.) There are two ways to overcome the problem: If the printer supports XON/XOFF flow control, have FreeBSD use it by specifying the TANDEM bit in the fs capability. If the printer supports carrier flow control, specify the MDMBUF bit in the fs capability. Make sure the cable connecting the printer to the computer is correctly wired for carrier flow control. If the printer does not support any flow control, use some combination of the NLDELAY, TBDELAY, CRDELAY, VTDELAY, and BSDELAY bits in the fs capability to add appropriate delays to the stream of data sent to the printer. It printed garbage. The printer printed what appeared to be random garbage, but not the desired text. This is usually another symptom of incorrect communications parameters with a serial printer. Double-check the bps rate in the br capability, and the parity bits in the fs and fc capabilities; make sure the printer is using the same settings as specified in the /etc/printcap file. Nothing happened. If nothing happened, the problem is probably within FreeBSD and not the hardware. Add the log file (lf) capability to the entry for the printer you are debugging in the /etc/printcap file. For example, here is the entry for rattan, with the lf capability: rattan|line|diablo|lp|Diablo 630 Line Printer:\ :sh:sd=/var/spool/lpd/rattan:\ :lp=/dev/lpt0:\ :if=/usr/local/libexec/if-simple:\ :lf=/var/log/rattan.log Then, try printing again. Check the log file (in our example, /var/log/rattan.log) to see any error messages that might appear. Based on the messages you see, try to correct the problem. If you do not specify a lf capability, LPD uses /dev/console as a default. This section tells you how to use printers you have setup with FreeBSD. Here is an overview of the user-level commands: lpr Print jobs lpq Check printer queues lprm Remove jobs from a printer's queue There is also an administrative command, lpc, described in the section Administrating the LPD Spooler, used to control printers and their queues. All three of the commands lpr, lprm, and lpq accept an option -P printer-name to specify on which printer/queue to operate, as listed in the /etc/printcap file. This enables you to submit, remove, and check on jobs for various printers. If you do not use the -P option, then these commands use the printer specified in the PRINTER environment variable. Finally, if you do not have a PRINTER environment variable, these commands default to the printer named lp. Hereafter, the terminology default printer means the printer named in the PRINTER environment variable, or the printer named lp when there is no PRINTER environment variable. To print files, type: &prompt.user; lpr filename ... This prints each of the listed files to the default printer. If you list no files, lpr reads data to print from standard input. For example, this command prints some important system files: &prompt.user; lpr /etc/host.conf /etc/hosts.equiv To select a specific printer, type: &prompt.user; lpr -P printer-name filename ... This example prints a long listing of the current directory to the printer named rattan: &prompt.user; ls -l | lpr -P rattan Because no files were listed for the lpr command, lpr read the data to print from standard input, which was the output of the ls -l command. The lpr command can also accept a wide variety of options to control formatting, apply file conversions, generate multiple copies, and so forth. For more information, see the section Printing Options. When you print with lpr, the data you wish to print is put together in a package called a “print job”, which is sent to the LPD spooling system. Each printer has a queue of jobs, and your job waits in that queue along with other jobs from yourself and from other users. The printer prints those jobs in a first-come, first-served order. To display the queue for the default printer, type lpq. For a specific printer, use the -P option. For example, the command &prompt.user; lpq -P bamboo shows the queue for the printer named bamboo. Here is an example of the output of the lpq command: bamboo is ready and printing Rank Owner Job Files Total Size active kelly 9 /etc/host.conf, /etc/hosts.equiv 88 bytes 2nd kelly 10 (standard input) 1635 bytes 3rd mary 11 ... 78519 bytes This shows three jobs in the queue for bamboo. The first job, submitted by user kelly, got assigned “job number” 9. Every job for a printer gets a unique job number. Most of the time you can ignore the job number, but you will need it if you want to cancel the job; see section Removing Jobs for details. Job number nine consists of two files; multiple files given on the lpr command line are treated as part of a single job. It is the currently active job (note the word active under the “Rank” column), which means the printer should be currently printing that job. The second job consists of data passed as the standard input to the lpr command. The third job came from user mary; it is a much larger job. The pathname of the files she's trying to print is too long to fit, so the lpq command just shows three dots. The very first line of the output from lpq is also useful: it tells what the printer is currently doing (or at least what LPD thinks the printer is doing). The lpq command also support a -l option to generate a detailed long listing. Here is an example of lpq -l: waiting for bamboo to become ready (offline ?) kelly: 1st [job 009rose] /etc/host.conf 73 bytes /etc/hosts.equiv 15 bytes kelly: 2nd [job 010rose] (standard input) 1635 bytes mary: 3rd [job 011rose] /home/orchid/mary/research/venus/alpha-regio/mapping 78519 bytes If you change your mind about printing a job, you can remove the job from the queue with the lprm command. Often, you can even use lprm to remove an active job, but some or all of the job might still get printed. To remove a job from the default printer, first use lpq to find the job number. Then type: &prompt.user; lprm job-number To remove the job from a specific printer, add the -P option. The following command removes job number 10 from the queue for the printer bamboo: &prompt.user; lprm -P bamboo 10 The lprm command has a few shortcuts: lprm - Removes all jobs (for the default printer) belonging to you. lprm user Removes all jobs (for the default printer) belonging to user. The superuser can remove other users' jobs; you can remove only your own jobs. lprm With no job number, user name, or - appearing on the command line, lprm removes the currently active job on the default printer, if it belongs to you. The superuser can remove any active job. Just use the -P option with the above shortcuts to operate on a specific printer instead of the default. For example, the following command removes all jobs for the current user in the queue for the printer named rattan: &prompt.user; lprm -P rattan - If you are working in a networked environment, lprm will let you remove jobs only from the host from which the jobs were submitted, even if the same printer is available from other hosts. The following command sequence demonstrates this: &prompt.user; lpr -P rattan myfile &prompt.user; rlogin orchid &prompt.user; lpq -P rattan Rank Owner Job Files Total Size active seeyan 12 ... 49123 bytes 2nd kelly 13 myfile 12 bytes &prompt.user; lprm -P rattan 13 rose: Permission denied &prompt.user; logout &prompt.user; lprm -P rattan 13 dfA013rose dequeued cfA013rose dequeued The lpr command supports a number of options that control formatting text, converting graphic and other file formats, producing multiple copies, handling of the job, and more. This section describes the options. The following lpr options control formatting of the files in the job. Use these options if the job does not contain plain text or if you want plain text formatted through the pr utility. For example, the following command prints a DVI file (from the TeX typesetting system) named fish-report.dvi to the printer named bamboo: &prompt.user; lpr -P bamboo -d fish-report.dvi These options apply to every file in the job, so you cannot mix (say) DVI and ditroff files together in a job. Instead, submit the files as separate jobs, using a different conversion option for each job. All of these options except -p and -T require conversion filters installed for the destination printer. For example, the -d option requires the DVI conversion filter. Section Conversion Filters gives details. -c Print cifplot files. -d Print DVI files. -f Print FORTRAN text files. -g Print plot data. -i number Indent the output by number columns; if you omit number, indent by 8 columns. This option works only with certain conversion filters. Do not put any space between the -i and the number. -l Print literal text data, including control characters. -n Print ditroff (device independent troff) data. -p Format plain text with pr before printing. See pr1 for more information. -T title Use title on the pr header instead of the file name. This option has effect only when used with the -p option. -t Print troff data. -v Print raster data. Here is an example: this command prints a nicely formatted version of the ls manual page on the default printer: &prompt.user; zcat /usr/share/man/man1/ls.1.gz | troff -t -man | lpr -t The zcat command uncompresses the source of the ls manual page and passes it to the troff command, which formats that source and makes GNU troff output and passes it to lpr, which submits the job to the LPD spooler. Because we used the -t option to lpr, the spooler will convert the GNU troff output into a format the default printer can understand when it prints the job. The following options to lpr tell LPD to handle the job specially: -# copies Produce a number of copies of each file in the job instead of just one copy. An administrator may disable this option to reduce printer wear-and-tear and encourage photocopier usage. See section Restricting Multiple Copies. This example prints three copies of parser.c followed by three copies of parser.h to the default printer: &prompt.user; lpr -#3 parser.c parser.h -m Send mail after completing the print job. With this option, the LPD system will send mail to your account when it finishes handling your job. In its message, it will tell you if the job completed successfully or if there was an error, and (often) what the error was. -s Do not copy the files to the spooling directory, but make symbolic links to them instead. If you are printing a large job, you probably want to use this option. It saves space in the spooling directory (your job might overflow the free space on the filesystem where the spooling directory resides). It saves time as well since LPD will not have to copy each and every byte of your job to the spooling directory. There is a drawback, though: since LPD will refer to the original files directly, you cannot modify or remove them until they have been printed. If you are printing to a remote printer, LPD will eventually have to copy files from the local host to the remote host, so the -s option will save space only on the local spooling directory, not the remote. It is still useful, though. -r Remove the files in the job after copying them to the spooling directory, or after printing them with the -s option. Be careful with this option! These options to lpr adjust the text that normally appears on a job's header page. If header pages are suppressed for the destination printer, these options have no effect. See section Header Pages for information about setting up header pages. -C text Replace the hostname on the header page with text. The hostname is normally the name of the host from which the job was submitted. -J text Replace the job name on the header page with text. The job name is normally the name of the first file of the job, or stdin if you are printing standard input. -h Do not print any header page. At some sites, this option may have no effect due to the way header pages are generated. See Header Pages for details. As an administrator for your printers, you have had to install, set up, and test them. Using the lpc command, you can interact with your printers in yet more ways. With lpc, you can Start and stop the printers Enable and disable their queues Rearrange the order of the jobs in each queue. First, a note about terminology: if a printer is stopped, it will not print anything in its queue. Users can still submit jobs, which will wait in the queue until the printer is started or the queue is cleared. If a queue is disabled, no user (except root) can submit jobs for the printer. An enabled queue allows jobs to be submitted. A printer can be started for a disabled queue, in which case it will continue to print jobs in the queue until the queue is empty. In general, you have to have root privileges to use the lpc command. Ordinary users can use the lpc command to get printer status and to restart a hung printer only. Here is a summary of the lpc commands. Most of the commands takes a printer-name argument to tell on which printer to operate. You can use all for the printer-name to mean all printers listed in /etc/printcap. abort printer-name Cancel the current job and stop the printer. Users can still submit jobs if the queue's enabled. clean printer-name Remove old files from the printer's spooling directory. Occasionally, the files that make up a job are not properly removed by LPD, particularly if there have been errors during printing or a lot of administrative activity. This command finds files that do not belong in the spooling directory and removes them. disable printer-name Disable queuing of new jobs. If the printer's started, it will continue to print any jobs remaining in the queue. The superuser (root) can always submit jobs, even to a disabled queue. This command is useful while you are testing a new printer or filter installation: disable the queue and submit jobs as root. Other users will not be able to submit jobs until you complete your testing and re-enable the queue with the enable command. down printer-name message Take a printer down. Equivalent to disable followed by stop. The message appears as the printer's status whenever a user checks the printer's queue with lpq or status with lpc status. enable printer-name Enable the queue for a printer. Users can submit jobs but the printer will not print anything until it is started. help command-name Print help on the command command-name. With no command-name, print a summary of the commands available. restart printer-name Start the printer. Ordinary users can use this command if some extraordinary circumstance hangs LPD, but they cannot start a printer stopped with either the stop or down commands. The restart command is equivalent to abort followed by start. start printer-name Start the printer. The printer will print jobs in its queue. stop printer-name Stop the printer. The printer will finish the current job and will not print anything else in its queue. Even though the printer is stopped, users can still submit jobs to an enabled queue. topq printer-name job-or-username Rearrange the queue for printer-name by placing the jobs with the listed job numbers or the jobs belonging to username at the top of the queue. For this command, you cannot use all as the printer-name. up printer-name Bring a printer up; the opposite of the down command. Equivalent to start followed by enable. lpc accepts the above commands on the command line. If you do not enter any commands, lpc enters an interactive mode, where you can enter commands until you type exit, quit, or end-of-file. This section describes filters for printing specially formatted files, header pages, printing across networks, and restricting and accounting for printer usage. Although LPD handles network protocols, queuing, access control, and other aspects of printing, most of the real work happens in the filters. Filters are programs that communicate with the printer and handle its device dependencies and special requirements. In the simple printer setup, we installed a plain text filter—an extremely simple one that should work with most printers (section Installing the Text Filter). However, in order to take advantage of format conversion, printer accounting, specific printer quirks, and so on, you should understand how filters work. It will ultimately be the filter's responsibility to handle these aspects. And the bad news is that most of the time you have to provide filters yourself. The good news is that many are generally available; when they are not, they are usually easy to write. Also, FreeBSD comes with one, /usr/libexec/lpr/lpf, that works with many printers that can print plain text. (It handles backspacing and tabs in the file, and does accounting, but that is about all it does.) There are also several filters and filter components in the FreeBSD ports collection. Here is what you will find in this section: Section How Filters Work, tries to give an overview of a filter's role in the printing process. You should read this section to get an understanding of what is happening “under the hood” when LPD uses filters. This knowledge could help you anticipate and debug problems you might encounter as you install more and more filters on each of your printers. LPD expects every printer to be able to print plain text by default. This presents a problem for PostScript (or other language-based printers) which cannot directly print plain text. Section Accommodating Plain Text Jobs on PostScript Printers tells you what you should do to overcome this problem. I recommend reading this section if you have a PostScript printer. PostScript is a popular output format for many programs. Even some people (myself included) write PostScript code directly. But PostScript printers are expensive. Section Simulating PostScript on Non-PostScript Printers tells how you can further modify a printer's text filter to accept and print PostScript data on a non-PostScript printer. I recommend reading this section if you do not have a PostScript printer. Section Conversion Filters tells about a way you can automate the conversion of specific file formats, such as graphic or typesetting data, into formats your printer can understand. After reading this section, you should be able to set up your printers such that users can type lpr -t to print troff data, or lpr -d to print TeX DVI data, or lpr -v to print raster image data, and so forth. I recommend reading this section. Section Output Filters tells all about a not often used feature of LPD: output filters. Unless you are printing header pages (see Header Pages), you can probably skip that section altogether. Section lpf: a Text Filter describes lpf, a fairly complete if simple text filter for line printers (and laser printers that act like line printers) that comes with FreeBSD. If you need a quick way to get printer accounting working for plain text, or if you have a printer which emits smoke when it sees backspace characters, you should definitely consider lpf. As mentioned before, a filter is an executable program started by LPD to handle the device-dependent part of communicating with the printer. When LPD wants to print a file in a job, it starts a filter program. It sets the filter's standard input to the file to print, its standard output to the printer, and its standard error to the error logging file (specified in the lf capability in /etc/printcap, or /dev/console by default). Which filter LPD starts and the filter's arguments depend on what is listed in the /etc/printcap file and what arguments the user specified for the job on the lpr command line. For example, if the user typed lpr -t, LPD would start the troff filter, listed in the tf capability for the destination printer. If the user wanted to print plain text, it would start the if filter (this is mostly true: see Output Filters for details). There are three kinds of filters you can specify in /etc/printcap: The text filter, confusingly called the input filter in LPD documentation, handles regular text printing. Think of it as the default filter. LPD expects every printer to be able to print plain text by default, and it is the text filter's job to make sure backspaces, tabs, or other special characters do not confuse the printer. If you are in an environment where you have to account for printer usage, the text filter must also account for pages printed, usually by counting the number of lines printed and comparing that to the number of lines per page the printer supports. The text filter is started with the following argument list: filter-name -c -wwidth -llength -iindent -n login -h host acct-file where -c appears if the job's submitted with lpr -l width is the value from the pw (page width) capability specified in /etc/printcap, default 132 length is the value from the pl (page length) capability, default 66 indent is the amount of the indentation from lpr -i, default 0 login is the account name of the user printing the file host is the host name from which the job was submitted acct-file is the name of the accounting file from the af capability. A conversion filter converts a specific file format into one the printer can render onto paper. For example, ditroff typesetting data cannot be directly printed, but you can install a conversion filter for ditroff files to convert the ditroff data into a form the printer can digest and print. Section Conversion Filters tells all about them. Conversion filters also need to do accounting, if you need printer accounting. Conversion filters are started with the following arguments: filter-name -xpixel-width -ypixel-height -n login -h host acct-file where pixel-width is the value from the px capability (default 0) and pixel-height is the value from the py capability (default 0). The output filter is used only if there is no text filter, or if header pages are enabled. In my experience, output filters are rarely used. Section Output Filters describe them. There are only two arguments to an output filter: filter-name -wwidth -llength which are identical to the text filters -w and -l arguments. Filters should also exit with the following exit status: exit 0 If the filter printed the file successfully. exit 1 If the filter failed to print the file but wants LPD to try to print the file again. LPD will restart a filter if it exits with this status. exit 2 If the filter failed to print the file and does not want LPD to try again. LPD will throw out the file. The text filter that comes with the FreeBSD release, /usr/libexec/lpr/lpf, takes advantage of the page width and length arguments to determine when to send a form feed and how to account for printer usage. It uses the login, host, and accounting file arguments to make the accounting entries. If you are shopping for filters, see if they are LPD-compatible. If they are, they must support the argument lists described above. If you plan on writing filters for general use, then have them support the same argument lists and exit codes. If you are the only user of your computer and PostScript (or other language-based) printer, and you promise to never send plain text to your printer and to never use features of various programs that will want to send plain text to your printer, then you do not need to worry about this section at all. But, if you would like to send both PostScript and plain text jobs to the printer, then you are urged to augment your printer setup. To do so, we have the text filter detect if the arriving job is plain text or PostScript. All PostScript jobs must start with %! (for other printer languages, see your printer documentation). If those are the first two characters in the job, we have PostScript, and can pass the rest of the job directly. If those are not the first two characters in the file, then the filter will convert the text into PostScript and print the result. How do we do this? If you have got a serial printer, a great way to do it is to install lprps. lprps is a PostScript printer filter which performs two-way communication with the printer. It updates the printer's status file with verbose information from the printer, so users and administrators can see exactly what the state of the printer is (such as toner low or paper jam). But more importantly, it includes a program called psif which detects whether the incoming job is plain text and calls textps (another program that comes with lprps) to convert it to PostScript. It then uses lprps to send the job to the printer. lprps is part of the FreeBSD ports collection (see The Ports Collection). You can fetch, build and install it yourself, of course. After installing lprps, just specify the pathname to the psif program that is part of lprps. If you installed lprps from the ports collection, use the following in the serial PostScript printer's entry in /etc/printcap: :if=/usr/local/libexec/psif: You should also specify the rw capability; that tells LPD to open the printer in read-write mode. If you have a parallel PostScript printer (and therefore cannot use two-way communication with the printer, which lprps needs), you can use the following shell script as the text filter: #!/bin/sh # # psif - Print PostScript or plain text on a PostScript printer # Script version; NOT the version that comes with lprps # Installed in /usr/local/libexec/psif # read first_line first_two_chars=`expr "$first_line" : '\(..\)'` if [ "$first_two_chars" = "%!" ]; then # # PostScript job, print it. # echo $first_line && cat && printf "\004" && exit 0 exit 2 else # # Plain text, convert it, then print it. # ( echo $first_line; cat ) | /usr/local/bin/textps && printf "\004" && exit 0 exit 2 fi In the above script, textps is a program we installed separately to convert plain text to PostScript. You can use any text-to-PostScript program you wish. The FreeBSD ports collection (see The Ports Collection) includes a full featured text-to-PostScript program called a2ps that you might want to investigate. PostScript is the de facto standard for high quality typesetting and printing. PostScript is, however, an expensive standard. Thankfully, Alladin Enterprises has a free PostScript work-alike called Ghostscript that runs with FreeBSD. Ghostscript can read most PostScript files and can render their pages onto a variety of devices, including many brands of non-PostScript printers. By installing Ghostscript and using a special text filter for your printer, you can make your non-PostScript printer act like a real PostScript printer. Ghostscript should be in the FreeBSD ports collection, if you would like to install it from there. You can fetch, build, and install it quite easily yourself, as well. To simulate PostScript, we have the text filter detect if it is printing a PostScript file. If it is not, then the filter will pass the file directly to the printer; otherwise, it will use Ghostscript to first convert the file into a format the printer will understand. Here is an example: the following script is a text filter for Hewlett Packard DeskJet 500 printers. For other printers, substitute the -sDEVICE argument to the gs (Ghostscript) command. (Type gs -h to get a list of devices the current installation of Ghostscript supports.) #!/bin/sh # # ifhp - Print Ghostscript-simulated PostScript on a DeskJet 500 # Installed in /usr/local/libexec/hpif # # Treat LF as CR+LF: # printf "\033&k2G" || exit 2 # # Read first two characters of the file # read first_line first_two_chars=`expr "$first_line" : '\(..\)'` if [ "$first_two_chars" = "%!" ]; then # # It is PostScript; use Ghostscript to scan-convert and print it # /usr/local/bin/gs -dSAFER -dNOPAUSE -q -sDEVICE=djet500 -sOutputFile=- - \ && exit 0 else # # Plain text or HP/PCL, so just print it directly; print a form # at the end to eject the last page. # echo $first_line && cat && printf "\f" && exit 0 fi exit 2 Finally, you need to notify LPD of the filter via the if capability: :if=/usr/local/libexec/hpif: That is it. You can type lpr plain.text and lpr whatever.ps and both should print successfully. After completing the simple setup described in Simple Printer Setup, the first thing you will probably want to do is install conversion filters for your favorite file formats (besides plain ASCII text). Conversion filters make printing various kinds of files easy. As an example, suppose we do a lot of work with the TeX typesetting system, and we have a PostScript printer. Every time we generate a DVI file from TeX, we cannot print it directly until we convert the DVI file into PostScript. The command sequence goes like this: &prompt.user; dvips seaweed-analysis.dvi &prompt.user; lpr seaweed-analysis.ps By installing a conversion filter for DVI files, we can skip the hand conversion step each time by having LPD do it for us. Now, each time we get a DVI file, we are just one step away from printing it: &prompt.user; lpr -d seaweed-analysis.dvi We got LPD to do the DVI file conversion for us by specifying the -d option. Section Formatting and Conversion Options lists the conversion options. For each of the conversion options you want a printer to support, install a conversion filter and specify its pathname in /etc/printcap. A conversion filter is like the text filter for the simple printer setup (see section Installing the Text Filter) except that instead of printing plain text, the filter converts the file into a format the printer can understand. You should install the conversion filters you expect to use. If you print a lot of DVI data, then a DVI conversion filter is in order. If you have got plenty of troff to print out, then you probably want a troff filter. The following table summarizes the filters that LPD works with, their capability entries for the /etc/printcap file, and how to invoke them with the lpr command: File type /etc/printcap capability lpr option cifplot cf -c DVI df -d plot gf -g ditroff nf -n FORTRAN text rf -f troff rf -f raster vf -v plain text if none, -p, or -l In our example, using lpr -d means the printer needs a df capability in its entry in /etc/printcap. Despite what others might contend, formats like FORTRAN text and plot are probably obsolete. At your site, you can give new meanings to these or any of the formatting options just by installing custom filters. For example, suppose you would like to directly print Printerleaf files (files from the Interleaf desktop publishing program), but will never print plot files. You could install a Printerleaf conversion filter under the gf capability and then educate your users that lpr -g mean “print Printerleaf files.” Since conversion filters are programs you install outside of the base FreeBSD installation, they should probably go under /usr/local. The directory /usr/local/libexec is a popular location, since they are specialized programs that only LPD will run; regular users should not ever need to run them. To enable a conversion filter, specify its pathname under the appropriate capability for the destination printer in /etc/printcap. In our example, we will add the DVI conversion filter to the entry for the printer named bamboo. Here is the example /etc/printcap file again, with the new df capability for the printer bamboo. # # /etc/printcap for host rose - added df filter for bamboo # rattan|line|diablo|lp|Diablo 630 Line Printer:\ :sh:sd=/var/spool/lpd/rattan:\ :lp=/dev/lpt0:\ :if=/usr/local/libexec/if-simple: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh:sd=/var/spool/lpd/bamboo:\ :lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\ :if=/usr/local/libexec/psif:\ :df=/usr/local/libexec/psdf: The DVI filter is a shell script named /usr/local/libexec/psdf. Here is that script: #!bin/sh # # psdf - DVI to PostScript printer filter # Installed in /usr/local/libexec/psdf # # Invoked by lpd when user runs lpr -d # exec /usr/local/bin/dvips -f | /usr/local/libexec/lprps "$@" This script runs dvips in filter mode (the -f argument) on standard input, which is the job to print. It then starts the PostScript printer filter lprps (see section Accommodating Plain Text Jobs on PostScript Printers) with the arguments LPD passed to this script. lprps will use those arguments to account for the pages printed. Since there is no fixed set of steps to install conversion filters, let me instead provide more examples. Use these as guidance to making your own filters. Use them directly, if appropriate. This example script is a raster (well, GIF file, actually) conversion filter for a Hewlett Packard LaserJet III-Si printer: #!/bin/sh # # hpvf - Convert GIF files into HP/PCL, then print # Installed in /usr/local/libexec/hpvf PATH=/usr/X11R6/bin:$PATH; export PATH giftopnm | ppmtopgm | pgmtopbm | pbmtolj -resolution 300 \ && exit 0 \ || exit 2 It works by converting the GIF file into a portable anymap, converting that into a portable graymap, converting that into a portable bitmap, and converting that into LaserJet/PCL-compatible data. Here is the /etc/printcap file with an entry for a printer using the above filter: # # /etc/printcap for host orchid # teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\ :lp=/dev/lpt0:sh:sd=/var/spool/lpd/teak:mx#0:\ :if=/usr/local/libexec/hpif:\ :vf=/usr/local/libexec/hpvf: The following script is a conversion filter for troff data from the groff typesetting system for the PostScript printer named bamboo: #!/bin/sh # # pstf - Convert groff's troff data into PS, then print. # Installed in /usr/local/libexec/pstf # exec grops | /usr/local/libexec/lprps "$@" The above script makes use of lprps again to handle the communication with the printer. If the printer were on a parallel port, we would use this script instead: #!/bin/sh # # pstf - Convert groff's troff data into PS, then print. # Installed in /usr/local/libexec/pstf # exec grops That is it. Here is the entry we need to add to /etc/printcap to enable the filter: :tf=/usr/local/libexec/pstf: Here is an example that might make old hands at FORTRAN blush. It is a FORTRAN-text filter for any printer that can directly print plain text. We will install it for the printer teak: #!/bin/sh # # hprf - FORTRAN text filter for LaserJet 3si: # Installed in /usr/local/libexec/hprf # printf "\033&k2G" && fpr && printf "\f" && exit 0 exit 2 And we will add this line to the /etc/printcap for the printer teak to enable this filter: :rf=/usr/local/libexec/hprf: Here is one final, somewhat complex example. We will add a DVI filter to the LaserJet printer teak introduced earlier. First, the easy part: updating /etc/printcap with the location of the DVI filter: :df=/usr/local/libexec/hpdf: Now, for the hard part: making the filter. For that, we need a DVI-to-LaserJet/PCL conversion program. The FreeBSD ports collection (see The Ports Collection) has one: dvi2xx is the name of the package. Installing this package gives us the program we need, dvilj2p, which converts DVI into LaserJet IIp, LaserJet III, and LaserJet 2000 compatible codes. dvilj2p makes the filter hpdf quite complex since dvilj2p cannot read from standard input. It wants to work with a filename. What is worse, the filename has to end in .dvi so using /dev/fd/0 for standard input is problematic. We can get around that problem by linking (symbolically) a temporary file name (one that ends in .dvi) to /dev/fd/0, thereby forcing dvilj2p to read from standard input. The only other fly in the ointment is the fact that we cannot use /tmp for the temporary link. Symbolic links are owned by user and group bin. The filter runs as user daemon. And the /tmp directory has the sticky bit set. The filter can create the link, but it will not be able clean up when done and remove it since the link will belong to a different user. Instead, the filter will make the symbolic link in the current working directory, which is the spooling directory (specified by the sd capability in /etc/printcap). This is a perfect place for filters to do their work, especially since there is (sometimes) more free disk space in the spooling directory than under /tmp. Here, finally, is the filter: #!/bin/sh # # hpdf - Print DVI data on HP/PCL printer # Installed in /usr/local/libexec/hpdf PATH=/usr/local/bin:$PATH; export PATH # # Define a function to clean up our temporary files. These exist # in the current directory, which will be the spooling directory # for the printer. # cleanup() { rm -f hpdf$$.dvi } # # Define a function to handle fatal errors: print the given message # and exit 2. Exiting with 2 tells LPD to do not try to reprint the # job. # fatal() { echo "$@" 1>&2 cleanup exit 2 } # # If user removes the job, LPD will send SIGINT, so trap SIGINT # (and a few other signals) to clean up after ourselves. # trap cleanup 1 2 15 # # Make sure we are not colliding with any existing files. # cleanup # # Link the DVI input file to standard input (the file to print). # ln -s /dev/fd/0 hpdf$$.dvi || fatal "Cannot symlink /dev/fd/0" # # Make LF = CR+LF # printf "\033&k2G" || fatal "Cannot initialize printer" # # Convert and print. Return value from dvilj2p does not seem to be # reliable, so we ignore it. # dvilj2p -M1 -q -e- dfhp$$.dvi # # Clean up and exit # cleanup exit 0 All these conversion filters accomplish a lot for your printing environment, but at the cost forcing the user to specify (on the lpr command line) which one to use. If your users are not particularly computer literate, having to specify a filter option will become annoying. What is worse, though, is that an incorrectly specified filter option may run a filter on the wrong type of file and cause your printer to spew out hundreds of sheets of paper. Rather than install conversion filters at all, you might want to try having the text filter (since it is the default filter) detect the type of file it has been asked to print and then automatically run the right conversion filter. Tools such as file can be of help here. Of course, it will be hard to determine the differences between some file types—and, of course, you can still provide conversion filters just for them. The FreeBSD ports collection has a text filter that performs automatic conversion called apsfilter. It can detect plain text, PostScript, and DVI files, run the proper conversions, and print. The LPD spooling system supports one other type of filter that we have not yet explored: an output filter. An output filter is intended for printing plain text only, like the text filter, but with many simplifications. If you are using an output filter but no text filter, then: LPD starts an output filter once for the entire job instead of once for each file in the job. LPD does not make any provision to identify the start or the end of files within the job for the output filter. LPD does not pass the user's login or host to the filter, so it is not intended to do accounting. In fact, it gets only two arguments: filter-name -wwidth -llength Where width is from the pw capability and length is from the pl capability for the printer in question. Do not be seduced by an output filter's simplicity. If you would like each file in a job to start on a different page an output filter will not work. Use a text filter (also known as an input filter); see section Installing the Text Filter. Furthermore, an output filter is actually more complex in that it has to examine the byte stream being sent to it for special flag characters and must send signals to itself on behalf of LPD. However, an output filter is necessary if you want header pages and need to send escape sequences or other initialization strings to be able to print the header page. (But it is also futile if you want to charge header pages to the requesting user's account, since LPD does not give any user or host information to the output filter.) On a single printer, LPD allows both an output filter and text or other filters. In such cases, LPD will start the output filter to print the header page (see section Header Pages) only. LPD then expects the output filter to stop itself by sending two bytes to the filter: ASCII 031 followed by ASCII 001. When an output filter sees these two bytes (031, 001), it should stop by sending SIGSTOP to itself. When LPD's done running other filters, it will restart the output filter by sending SIGCONT to it. If there is an output filter but no text filter and LPD is working on a plain text job, LPD uses the output filter to do the job. As stated before, the output filter will print each file of the job in sequence with no intervening form feeds or other paper advancement, and this is probably not what you want. In almost all cases, you need a text filter. The program lpf, which we introduced earlier as a text filter, can also run as an output filter. If you need a quick-and-dirty output filter but do not want to write the byte detection and signal sending code, try lpf. You can also wrap lpf in a shell script to handle any initialization codes the printer might require. The program /usr/libexec/lpr/lpf that comes with FreeBSD binary distribution is a text filter (input filter) that can indent output (job submitted with lpr -i), allow literal characters to pass (job submitted with lpr -l), adjust the printing position for backspaces and tabs in the job, and account for pages printed. It can also act like an output filter. lpf is suitable for many printing environments. And although it has no capability to send initialization sequences to a printer, it is easy to write a shell script to do the needed initialization and then execute lpf. In order for lpf to do page accounting correctly, it needs correct values filled in for the pw and pl capabilities in the /etc/printcap file. It uses these values to determine how much text can fit on a page and how many pages were in a user's job. For more information on printer accounting, see Accounting for Printer Usage. If you have lots of users, all of them using various printers, then you probably want to consider header pages as a necessary evil. Header pages, also known as banner or burst pages identify to whom jobs belong after they are printed. They are usually printed in large, bold letters, perhaps with decorative borders, so that in a stack of printouts they stand out from the real documents that comprise users' jobs. They enable users to locate their jobs quickly. The obvious drawback to a header page is that it is yet one more sheet that has to be printed for every job, their ephemeral usefulness lasting not more than a few minutes, ultimately finding themselves in a recycling bin or rubbish heap. (Note that header pages go with each job, not each file in a job, so the paper waste might not be that bad.) The LPD system can provide header pages automatically for your printouts if your printer can directly print plain text. If you have a PostScript printer, you will need an external program to generate the header page; see Header Pages on PostScript Printers. In the Simple Printer Setup, we turned off header pages by specifying sh (meaning “suppress header”) in the /etc/printcap file. To enable header pages for a printer, just remove the sh capability. Sounds too easy, right? You are right. You might have to provide an output filter to send initialization strings to the printer. Here is an example output filter for Hewlett Packard PCL-compatible printers: #!/bin/sh # # hpof - Output filter for Hewlett Packard PCL-compatible printers # Installed in /usr/local/libexec/hpof printf "\033&k2G" || exit 2 exec /usr/libexec/lpr/lpf Specify the path to the output filter in the of capability. See Output Filters for more information. Here is an example /etc/printcap file for the printer teak that we introduced earlier; we enabled header pages and added the above output filter: # # /etc/printcap for host orchid # teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\ :lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:\ :if=/usr/local/libexec/hpif:\ :vf=/usr/local/libexec/hpvf:\ :of=/usr/local/libexec/hpof: Now, when users print jobs to teak, they get a header page with each job. If users want to spend time searching for their printouts, they can suppress header pages by submitting the job with lpr -h; see Header Page Options for more lpr options. LPD prints a form feed character after the header page. If your printer uses a different character or sequence of characters to eject a page, specify them with the ff capability in /etc/printcap. By enabling header pages, LPD will produce a long header, a full page of large letters identifying the user, host, and job. Here is an example (kelly printed the job named outline from host rose): k ll ll k l l k l l k k eeee l l y y k k e e l l y y k k eeeeee l l y y kk k e l l y y k k e e l l y yy k k eeee lll lll yyy y y y y yyyy ll t l i t l oooo u u ttttt l ii n nnn eeee o o u u t l i nn n e e o o u u t l i n n eeeeee o o u u t l i n n e o o u uu t t l i n n e e oooo uuu u tt lll iii n n eeee r rrr oooo ssss eeee rr r o o s s e e r o o ss eeeeee r o o ss e r o o s s e e r oooo ssss eeee Job: outline Date: Sun Sep 17 11:04:58 1995 LPD appends a form feed after this text so the job starts on a new page (unless you have sf (suppress form feeds) in the destination printer's entry in /etc/printcap). If you prefer, LPD can make a short header; specify sb (short banner) in the /etc/printcap file. The header page will look like this: rose:kelly Job: outline Date: Sun Sep 17 11:07:51 1995 Also by default, LPD prints the header page first, then the job. To reverse that, specify hl (header last) in /etc/printcap. Using LPD's built-in header pages enforces a particular paradigm when it comes to printer accounting: header pages must be free of charge. Why? Because the output filter is the only external program that will have control when the header page is printed that could do accounting, and it is not provided with any user or host information or an accounting file, so it has no idea whom to charge for printer use. It is also not enough to just “add one page” to the text filter or any of the conversion filters (which do have user and host information) since users can suppress header pages with lpr -h. They could still be charged for header pages they did not print. Basically, lpr -h will be the preferred option of environmentally-minded users, but you cannot offer any incentive to use it. It is still not enough to have each of the filters generate their own header pages (thereby being able to charge for them). If users wanted the option of suppressing the header pages with lpr -h, they will still get them and be charged for them since LPD does not pass any knowledge of the -h option to any of the filters. So, what are your options? You can: Accept LPD's paradigm and make header pages free. Install an alternative to LPD, such as LPDng or PLP. Section Alternatives to the Standard Spooler tells more about other spooling software you can substitute for LPD. Write a smart output filter. Normally, an output filter is not meant to do anything more than initialize a printer or do some simple character conversion. It is suited for header pages and plain text jobs (when there is no text (input) filter). But, if there is a text filter for the plain text jobs, then LPD will start the output filter only for the header pages. And the output filter can parse the header page text that LPD generates to determine what user and host to charge for the header page. The only other problem with this method is that the output filter still does not know what accounting file to use (it is not passed the name of the file from the af capability), but if you have a well-known accounting file, you can hard-code that into the output filter. To facilitate the parsing step, use the sh (short header) capability in /etc/printcap. Then again, all that might be too much trouble, and users will certainly appreciate the more generous system administrator who makes header pages free. As described above, LPD can generate a plain text header page suitable for many printers. Of course, PostScript cannot directly print plain text, so the header page feature of LPD is useless—or mostly so. One obvious way to get header pages is to have every conversion filter and the text filter generate the header page. The filters should should use the user and host arguments to generate a suitable header page. The drawback of this method is that users will always get a header page, even if they submit jobs with lpr -h. Let us explore this method. The following script takes three arguments (user login name, host name, and job name) and makes a simple PostScript header page: #!/bin/sh # # make-ps-header - make a PostScript header page on stdout # Installed in /usr/local/libexec/make-ps-header # # # These are PostScript units (72 to the inch). Modify for A4 or # whatever size paper you are using: # page_width=612 page_height=792 border=72 # # Check arguments # if [ $# -ne 3 ]; then echo "Usage: `basename $0` <user> <host> <job>" 1>&2 exit 1 fi # # Save these, mostly for readability in the PostScript, below. # user=$1 host=$2 job=$3 date=`date` # # Send the PostScript code to stdout. # exec cat <<EOF %!PS % % Make sure we do not interfere with user's job that will follow % save % % Make a thick, unpleasant border around the edge of the paper. % $border $border moveto $page_width $border 2 mul sub 0 rlineto 0 $page_height $border 2 mul sub rlineto currentscreen 3 -1 roll pop 100 3 1 roll setscreen $border 2 mul $page_width sub 0 rlineto closepath 0.8 setgray 10 setlinewidth stroke 0 setgray % % Display user's login name, nice and large and prominent % /Helvetica-Bold findfont 64 scalefont setfont $page_width ($user) stringwidth pop sub 2 div $page_height 200 sub moveto ($user) show % % Now show the boring particulars % /Helvetica findfont 14 scalefont setfont /y 200 def [ (Job:) (Host:) (Date:) ] { 200 y moveto show /y y 18 sub def } forall /Helvetica-Bold findfont 14 scalefont setfont /y 200 def [ ($job) ($host) ($date) ] { 270 y moveto show /y y 18 sub def } forall % % That is it % restore showpage EOF Now, each of the conversion filters and the text filter can call this script to first generate the header page, and then print the user's job. Here is the DVI conversion filter from earlier in this document, modified to make a header page: #!/bin/sh # # psdf - DVI to PostScript printer filter # Installed in /usr/local/libexec/psdf # # Invoked by lpd when user runs lpr -d # orig_args="$@" fail() { echo "$@" 1>&2 exit 2 } while getopts "x:y:n:h:" option; do case $option in x|y) ;; # Ignore n) login=$OPTARG ;; h) host=$OPTARG ;; *) echo "LPD started `basename $0` wrong." 1>&2 exit 2 ;; esac done [ "$login" ] || fail "No login name" [ "$host" ] || fail "No host name" ( /usr/local/libexec/make-ps-header $login $host "DVI File" /usr/local/bin/dvips -f ) | eval /usr/local/libexec/lprps $orig_args Notice how the filter has to parse the argument list in order to determine the user and host name. The parsing for the other conversion filters is identical. The text filter takes a slightly different set of arguments, though (see section How Filters Work). As we have mentioned before, the above scheme, though fairly simple, disables the “suppress header page” option (the -h option) to lpr. If users wanted to save a tree (or a few pennies, if you charge for header pages), they would not be able to do so, since every filter's going to print a header page with every job. To allow users to shut off header pages on a per-job basis, you will need to use the trick introduced in section Accounting for Header Pages: write an output filter that parses the LPD-generated header page and produces a PostScript version. If the user submits the job with lpr -h, then LPD will not generate a header page, and neither will your output filter. Otherwise, your output filter will read the text from LPD and send the appropriate header page PostScript code to the printer. If you have a PostScript printer on a serial line, you can make use of lprps, which comes with an output filter, psof, which does the above. Note that psof does not charge for header pages. FreeBSD supports networked printing: sending jobs to remote printers. Networked printing generally refers to two different things: Accessing a printer attached to a remote host. You install a printer that has a conventional serial or parallel interface on one host. Then, you set up LPD to enable access to the printer from other hosts on the network. Section Printers Installed on Remote Hosts tells how to do this. Accessing a printer attached directly to a network. The printer has a network interface in addition (or in place of) a more conventional serial or parallel interface. Such a printer might work as follows: It might understand the LPD protocol and can even queue jobs from remote hosts. In this case, it acts just like a regular host running LPD. Follow the same procedure in section Printers Installed on Remote Hosts to set up such a printer. It might support a data stream network connection. In this case, you “attach” the printer to one host on the network by making that host responsible for spooling jobs and sending them to the printer. Section Printers with Networked Data Stream Interfaces gives some suggestions on installing such printers. The LPD spooling system has built-in support for sending jobs to other hosts also running LPD (or are compatible with LPD). This feature enables you to install a printer on one host and make it accessible from other hosts. It also works with printers that have network interfaces that understand the LPD protocol. To enable this kind of remote printing, first install a printer on one host, the printer host, using the simple printer setup described in Simple Printer Setup. Do any advanced setup in Advanced Printer Setup that you need. Make sure to test the printer and see if it works with the features of LPD you have enabled. Also ensure that the local host has authorization to use the LPD service in the remote host (see Restricting Jobs from Remote Printers). If you are using a printer with a network interface that is compatible with LPD, then the printer host in the discussion below is the printer itself, and the printer name is the name you configured for the printer. See the documentation that accompanied your printer and/or printer-network interface. Then, on the other hosts you want to have access to the printer, make an entry in their /etc/printcap files with the following: Name the entry anything you want. For simplicity, though, you probably want to use the same name and aliases as on the printer host. Leave the lp capability blank, explicitly (:lp=:). Make a spooling directory and specify its location in the sd capability. LPD will store jobs here before they get sent to the printer host. Place the name of the printer host in the rm capability. Place the printer name on the printer host in the rp capability. That is it. You do not need to list conversion filters, page dimensions, or anything else in the /etc/printcap file. Here is an example. The host rose has two printers, bamboo and rattan. We will enable users on the host orchid to print to those printers. Here is the /etc/printcap file for orchid (back from section Enabling Header Pages). It already had the entry for the printer teak; we have added entries for the two printers on the host rose: # # /etc/printcap for host orchid - added (remote) printers on rose # # # teak is local; it is connected directly to orchid: # teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\ :lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:\ :if=/usr/local/libexec/ifhp:\ :vf=/usr/local/libexec/vfhp:\ :of=/usr/local/libexec/ofhp: # # rattan is connected to rose; send jobs for rattan to rose: # rattan|line|diablo|lp|Diablo 630 Line Printer:\ :lp=:rm=rose:rp=rattan:sd=/var/spool/lpd/rattan: # # bamboo is connected to rose as well: # bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :lp=:rm=rose:rp=bamboo:sd=/var/spool/lpd/bamboo: Then, we just need to make spooling directories on orchid: &prompt.root; mkdir -p /var/spool/lpd/rattan /var/spool/lpd/bamboo &prompt.root; chmod 770 /var/spool/lpd/rattan /var/spool/lpd/bamboo &prompt.root; chown daemon.daemon /var/spool/lpd/rattan /var/spool/lpd/bamboo Now, users on orchid can print to rattan and bamboo. If, for example, a user on orchid typed &prompt.user; lpr -P bamboo -d sushi-review.dvi the LPD system on orchid would copy the job to the spooling directory /var/spool/lpd/bamboo and note that it was a DVI job. As soon as the host rose has room in its bamboo spooling directory, the two LPDs would transfer the file to rose. The file would wait in rose's queue until it was finally printed. It would be converted from DVI to PostScript (since bamboo is a PostScript printer) on rose. Often, when you buy a network interface card for a printer, you can get two versions: one which emulates a spooler (the more expensive version), or one which just lets you send data to it as if you were using a serial or parallel port (the cheaper version). This section tells how to use the cheaper version. For the more expensive one, see the previous section Printers Installed on Remote Hosts. The format of the /etc/printcap file lets you specify what serial or parallel interface to use, and (if you are using a serial interface), what baud rate, whether to use flow control, delays for tabs, conversion of newlines, and more. But there is no way to specify a connection to a printer that is listening on a TCP/IP or other network port. To send data to a networked printer, you need to develop a communications program that can be called by the text and conversion filters. Here is one such example: the script netprint takes all data on standard input and sends it to a network-attached printer. We specify the hostname of the printer as the first argument and the port number to which to connect as the second argument to netprint. Note that this supports one-way communication only (FreeBSD to printer); many network printers support two-way communication, and you might want to take advantage of that (to get printer status, perform accounting, etc.). #!/usr/bin/perl # # netprint - Text filter for printer attached to network # Installed in /usr/local/libexec/netprint # $#ARGV eq 1 || die "Usage: $0 <printer-hostname> <port-number>"; $printer_host = $ARGV[0]; $printer_port = $ARGV[1]; require 'sys/socket.ph'; ($ignore, $ignore, $protocol) = getprotobyname('tcp'); ($ignore, $ignore, $ignore, $ignore, $address) = gethostbyname($printer_host); $sockaddr = pack('S n a4 x8', &AF_INET, $printer_port, $address); socket(PRINTER, &PF_INET, &SOCK_STREAM, $protocol) || die "Can't create TCP/IP stream socket: $!"; connect(PRINTER, $sockaddr) || die "Can't contact $printer_host: $!"; while (<STDIN>) { print PRINTER; } exit 0; We can then use this script in various filters. Suppose we had a Diablo 750-N line printer connected to the network. The printer accepts data to print on port number 5100. The host name of the printer is scrivener. Here is the text filter for the printer: #!/bin/sh # # diablo-if-net - Text filter for Diablo printer `scrivener' listening # on port 5100. Installed in /usr/local/libexec/diablo-if-net # exec /usr/libexec/lpr/lpf "$@" | /usr/local/libexec/netprint scrivener 5100 This section gives information on restricting printer usage. The LPD system lets you control who can access a printer, both locally or remotely, whether they can print multiple copies, how large their jobs can be, and how large the printer queues can get. The LPD system makes it easy for users to print multiple copies of a file. Users can print jobs with lpr -#5 (for example) and get five copies of each file in the job. Whether this is a good thing is up to you. If you feel multiple copies cause unnecessary wear and tear on your printers, you can disable the -# option to lpr by adding the sc capability to the /etc/printcap file. When users submit jobs with the -# option, they will see: lpr: multiple copies are not allowed Note that if you have set up access to a printer remotely (see section Printers Installed on Remote Hosts), you need the sc capability on the remote /etc/printcap files as well, or else users will still be able to submit multiple-copy jobs by using another host. Here is an example. This is the /etc/printcap file for the host rose. The printer rattan is quite hearty, so we will allow multiple copies, but the laser printer bamboo's a bit more delicate, so we will disable multiple copies by adding the sc capability: # # /etc/printcap for host rose - restrict multiple copies on bamboo # rattan|line|diablo|lp|Diablo 630 Line Printer:\ :sh:sd=/var/spool/lpd/rattan:\ :lp=/dev/lpt0:\ :if=/usr/local/libexec/if-simple: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh:sd=/var/spool/lpd/bamboo:sc:\ :lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\ :if=/usr/local/libexec/psif:\ :df=/usr/local/libexec/psdf: Now, we also need to add the sc capability on the host orchid's /etc/printcap (and while we are at it, let us disable multiple copies for the printer teak): # # /etc/printcap for host orchid - no multiple copies for local # printer teak or remote printer bamboo teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\ :lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:sc:\ :if=/usr/local/libexec/ifhp:\ :vf=/usr/local/libexec/vfhp:\ :of=/usr/local/libexec/ofhp: rattan|line|diablo|lp|Diablo 630 Line Printer:\ :lp=:rm=rose:rp=rattan:sd=/var/spool/lpd/rattan: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :lp=:rm=rose:rp=bamboo:sd=/var/spool/lpd/bamboo:sc: By using the sc capability, we prevent the use of lpr -#, but that still does not prevent users from running lpr multiple times, or from submitting the same file multiple times in one job like this: &prompt.user; lpr forsale.sign forsale.sign forsale.sign forsale.sign forsale.sign There are many ways to prevent this abuse (including ignoring it) which you are free to explore. You can control who can print to what printers by using the UNIX group mechanism and the rg capability in /etc/printcap. Just place the users you want to have access to a printer in a certain group, and then name that group in the rg capability. Users outside the group (including root) will be greeted with lpr: Not a member of the restricted group if they try to print to the controlled printer. As with the sc (suppress multiple copies) capability, you need to specify rg on remote hosts that also have access to your printers, if you feel it is appropriate (see section Printers Installed on Remote Hosts). For example, we will let anyone access the printer rattan, but only those in group artists can use bamboo. Here is the familiar /etc/printcap for host rose: # # /etc/printcap for host rose - restricted group for bamboo # rattan|line|diablo|lp|Diablo 630 Line Printer:\ :sh:sd=/var/spool/lpd/rattan:\ :lp=/dev/lpt0:\ :if=/usr/local/libexec/if-simple: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh:sd=/var/spool/lpd/bamboo:sc:rg=artists:\ :lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\ :if=/usr/local/libexec/psif:\ :df=/usr/local/libexec/psdf: Let us leave the other example /etc/printcap file (for the host orchid) alone. Of course, anyone on orchid can print to bamboo. It might be the case that we only allow certain logins on orchid anyway, and want them to have access to the printer. Or not. There can be only one restricted group per printer. If you have many users accessing the printers, you probably need to put an upper limit on the sizes of the files users can submit to print. After all, there is only so much free space on the filesystem that houses the spooling directories, and you also need to make sure there is room for the jobs of other users. LPD enables you to limit the maximum byte size a file in a job can be with the mx capability. The units are in BUFSIZ blocks, which are 1024 bytes. If you put a zero for this capability, there will be no limit on file size. The limit applies to files in a job, and not the total job size. LPD will not refuse a file that is larger than the limit you place on a printer. Instead, it will queue as much of the file up to the limit, which will then get printed. The rest will be discarded. Whether this is correct behavior is up for debate. Let us add limits to our example printers rattan and bamboo. Since those artists' PostScript files tend to be large, we will limit them to five megabytes. We will put no limit on the plain text line printer: # # /etc/printcap for host rose # # # No limit on job size: # rattan|line|diablo|lp|Diablo 630 Line Printer:\ :sh:sd=/var/spool/lpd/rattan:\ :lp=/dev/lpt0:\ :if=/usr/local/libexec/if-simple: # # Limit of five megabytes: # bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh:sd=/var/spool/lpd/bamboo:sc:rg=artists:mx#5000:\ :lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:\ :if=/usr/local/libexec/psif:\ :df=/usr/local/libexec/psdf: Again, the limits apply to the local users only. If you have set up access to your printers remotely, remote users will not get those limits. You will need to specify the mx capability in the remote /etc/printcap files as well. See section Printers Installed on Remote Hosts for more information on remote printing. There is another specialized way to limit job sizes from remote printers; see section Restricting Jobs from Remote Printers. The LPD spooling system provides several ways to restrict print jobs submitted from remote hosts: Host restrictions You can control from which remote hosts a local LPD accepts requests with the files /etc/hosts.equiv and /etc/hosts.lpd. LPD checks to see if an incoming request is from a host listed in either one of these files. If not, LPD refuses the request. The format of these files is simple: one host name per line. Note that the file /etc/hosts.equiv is also used by the ruserok3 protocol, and affects programs like rsh and rcp, so be careful. For example, here is the /etc/hosts.lpd file on the host rose: orchid violet madrigal.fishbaum.de This means rose will accept requests from the hosts orchid, violet, and madrigal.fishbaum.de. If any other host tries to access rose's LPD, LPD will refuse them. Size restrictions You can control how much free space there needs to remain on the filesystem where a spooling directory resides. Make a file called minfree in the spooling directory for the local printer. Insert in that file a number representing how many disk blocks (512 bytes) of free space there has to be for a remote job to be accepted. This lets you insure that remote users will not fill your filesystem. You can also use it to give a certain priority to local users: they will be able to queue jobs long after the free disk space has fallen below the amount specified in the minfree file. For example, let us add a minfree file for the printer bamboo. We examine /etc/printcap to find the spooling directory for this printer; here is bamboo's entry: bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\ :sh:sd=/var/spool/lpd/bamboo:sc:rg=artists:mx#5000:\ :lp=/dev/ttyd5:fs#0x82000e1:xs#0x820:rw:mx#5000:\ :if=/usr/local/libexec/psif:\ :df=/usr/local/libexec/psdf: The spooling directory is the given in the sd capability. We will make three megabytes (which is 6144 disk blocks) the amount of free disk space that must exist on the filesystem for LPD to accept remote jobs: &prompt.root; echo 6144 > /var/spool/lpd/bamboo/minfree User restrictions You can control which remote users can print to local printers by specifying the rs capability in /etc/printcap. When rs appears in the entry for a locally-attached printer, LPD will accept jobs from remote hosts if the user submitting the job also has an account of the same login name on the local host. Otherwise, LPD refuses the job. This capability is particularly useful in an environment where there are (for example) different departments sharing a network, and some users transcend departmental boundaries. By giving them accounts on your systems, they can use your printers from their own departmental systems. If you would rather allow them to use only your printers and not your compute resources, you can give them “token” accounts, with no home directory and a useless shell like /usr/bin/false. So, you need to charge for printouts. And why not? Paper and ink cost money. And then there are maintenance costs—printers are loaded with moving parts and tend to break down. You have examined your printers, usage patterns, and maintenance fees and have come up with a per-page (or per-foot, per-meter, or per-whatever) cost. Now, how do you actually start accounting for printouts? Well, the bad news is the LPD spooling system does not provide much help in this department. Accounting is highly dependent on the kind of printer in use, the formats being printed, and your requirements in charging for printer usage. To implement accounting, you have to modify a printer's text filter (to charge for plain text jobs) and the conversion filters (to charge for other file formats), to count pages or query the printer for pages printed. You cannot get away with using the simple output filter, since it cannot do accounting. See section Filters. Generally, there are two ways to do accounting: Periodic accounting is the more common way, possibly because it is easier. Whenever someone prints a job, the filter logs the user, host, and number of pages to an accounting file. Every month, semester, year, or whatever time period you prefer, you collect the accounting files for the various printers, tally up the pages printed by users, and charge for usage. Then you truncate all the logging files, starting with a clean slate for the next period. Timely accounting is less common, probably because it is more difficult. This method has the filters charge users for printouts as soon as they use the printers. Like disk quotas, the accounting is immediate. You can prevent users from printing when their account goes in the red, and might provide a way for users to check and adjust their “print quotas.” But this method requires some database code to track users and their quotas. The LPD spooling system supports both methods easily: since you have to provide the filters (well, most of the time), you also have to provide the accounting code. But there is a bright side: you have enormous flexibility in your accounting methods. For example, you choose whether to use periodic or timely accounting. You choose what information to log: user names, host names, job types, pages printed, square footage of paper used, how long the job took to print, and so forth. And you do so by modifying the filters to save this information. FreeBSD comes with two programs that can get you set up with simple periodic accounting right away. They are the text filter lpf, described in section lpf: a Text Filter, and pac, a program to gather and total entries from printer accounting files. As mentioned in the section on filters (Filters), LPD starts the text and the conversion filters with the name of the accounting file to use on the filter command line. The filters can use this argument to know where to write an accounting file entry. The name of this file comes from the af capability in /etc/printcap, and if not specified as an absolute path, is relative to the spooling directory. LPD starts lpf with page width and length arguments (from the pw and pl capabilities). lpf uses these arguments to determine how much paper will be used. After sending the file to the printer, it then writes an accounting entry in the accounting file. The entries look like this: 2.00 rose:andy 3.00 rose:kelly 3.00 orchid:mary 5.00 orchid:mary 2.00 orchid:zhang You should use a separate accounting file for each printer, as lpf has no file locking logic built into it, and two lpfs might corrupt each other's entries if they were to write to the same file at the same time. A easy way to insure a separate accounting file for each printer is to use af=acct in /etc/printcap. Then, each accounting file will be in the spooling directory for a printer, in a file named acct. When you are ready to charge users for printouts, run the pac program. Just change to the spooling directory for the printer you want to collect on and type pac. You will get a dollar-centric summary like the following: Login pages/feet runs price orchid:kelly 5.00 1 $ 0.10 orchid:mary 31.00 3 $ 0.62 orchid:zhang 9.00 1 $ 0.18 rose:andy 2.00 1 $ 0.04 rose:kelly 177.00 104 $ 3.54 rose:mary 87.00 32 $ 1.74 rose:root 26.00 12 $ 0.52 total 337.00 154 $ 6.74 These are the arguments pac expects: -Pprinter Which printer to summarize. This option works only if there is an absolute path in the af capability in /etc/printcap. -c Sort the output by cost instead of alphabetically by user name. -m Ignore host name in the accounting files. With this option, user smith on host alpha is the same user smith on host gamma. Without, they are different users. -pprice Compute charges with price dollars per page or per foot instead of the price from the pc capability in /etc/printcap, or two cents (the default). You can specify price as a floating point number. -r Reverse the sort order. -s Make an accounting summary file and truncate the accounting file. name … Print accounting information for the given user names only. In the default summary that pac produces, you see the number of pages printed by each user from various hosts. If, at your site, host does not matter (because users can use any host), run pac -m, to produce the following summary: Login pages/feet runs price andy 2.00 1 $ 0.04 kelly 182.00 105 $ 3.64 mary 118.00 35 $ 2.36 root 26.00 12 $ 0.52 zhang 9.00 1 $ 0.18 total 337.00 154 $ 6.74 To compute the dollar amount due, pac uses the pc capability in the /etc/printcap file (default of 200, or 2 cents per page). Specify, in hundredths of cents, the price per page or per foot you want to charge for printouts in this capability. You can override this value when you run pac with the -p option. The units for the -p option are in dollars, though, not hundredths of cents. For example, &prompt.root; pac -p1.50 makes each page cost one dollar and fifty cents. You can really rake in the profits by using this option. Finally, running pac -s will save the summary information in a summary accounting file, which is named the same as the printer's accounting file, but with _sum appended to the name. It then truncates the accounting file. When you run pac again, it rereads the summary file to get starting totals, then adds information from the regular accounting file. In order to perform even remotely accurate accounting, you need to be able to determine how much paper a job uses. This is the essential problem of printer accounting. For plain text jobs, the problem's not that hard to solve: you count how many lines are in a job and compare it to how many lines per page your printer supports. Do not forget to take into account backspaces in the file which overprint lines, or long logical lines that wrap onto one or more additional physical lines. The text filter lpf (introduced in lpf: a Text Filter) takes into account these things when it does accounting. If you are writing a text filter which needs to do accounting, you might want to examine lpf's source code. How do you handle other file formats, though? Well, for DVI-to-LaserJet or DVI-to-PostScript conversion, you can have your filter parse the diagnostic output of dvilj or dvips and look to see how many pages were converted. You might be able to do similar things with other file formats and conversion programs. But these methods suffer from the fact that the printer may not actually print all those pages. For example, it could jam, run out of toner, or explode—and the user would still get charged. So, what can you do? There is only one sure way to do accurate accounting. Get a printer that can tell you how much paper it uses, and attach it via a serial line or a network connection. Nearly all PostScript printers support this notion. Other makes and models do as well (networked Imagen laser printers, for example). Modify the filters for these printers to get the page usage after they print each job and have them log accounting information based on that value only. There is no line counting nor error-prone file examination required. Of course, you can always be generous and make all printouts free. If you have been reading straight through this manual, by now you have learned just about everything there is to know about the LPD spooling system that comes with FreeBSD. You can probably appreciate many of its shortcomings, which naturally leads to the question: “What other spooling systems are out there (and work with FreeBSD)?” Unfortunately, I have located only two alternatives—and they are almost identical to each other! They are: PLP, the Portable Line Printer Spooler System PLP was based on software developed by Patrick Powell and then maintained by an Internet-wide group of developers. The main site for the software is at ftp://ftp.iona.ie/pub/plp. There is also a web page. It is quite similar to the BSD LPD spooler, but boasts a host of features, including: Better network support, including built-in support for networked printers, NIS-maintained printcaps, and NFS-mounted spooling directories Sophisticated queue management, allowing multiple printers on a queue, transfer of jobs between queues, and queue redirection Remote printer control functions Prioritization of jobs Expansive security and access options LPRng LPRng, which purportedly means “LPR: the Next Generation” is a complete rewrite of PLP. Patrick Powell and Justin Mason (the principal maintainer of PLP) collaborated to make LPRng. The main site for LPRng is ftp://dickory.sdsu.edu/pub/LPRng. I would like to thank the following people who have assisted in the development of this document: Daniel Eischen deischen@iworks.interworks.org For providing a plethora of HP filter programs for perusal. &a.jehamby; For the Ghostscript-to-HP filter. My wife, Mary Kelly urquhart@argyre.colorado.edu For allowing me to spend more time with FreeBSD than with her.