章 9. 列印

Typical FreeBSD text files contain only a single line feed character at the end of each line. These lines will "stairstep" on a standard printer:

A filter can convert the newline characters into carriage returns and newlines. The carriage returns make the printer return to the left after each line. Create /usr/local/libexec/lf2crlf with these contents:

Set the permissions and make it executable:

Modify /etc/printcap to use the new filter:

Test the filter by printing the same plain text file. The carriage returns will cause each line to start at the left side of the page.

GNUEnscript converts plain text files into nicely-formatted PostScript™ for printing on PostScript™ printers. It adds page numbers, wraps long lines, and provides numerous other features to make printed text files easier to read. Depending on the local paper size, install either print/enscript-letter or print/enscript-a4 from the Ports Collection.

Create /usr/local/libexec/enscript with these contents:

Set the permissions and make it executable:

Modify /etc/printcap to use the new filter:

Test the filter by printing a plain text file.

Many programs produce PostScript™ documents. However, inexpensive printers often only understand plain text or PCL. This filter converts PostScript™ files to PCL before sending them to the printer.

由 Port 套件集安裝 Ghostscript PostScript™ 直譯器，print/ghostscript9-base。

Create /usr/local/libexec/ps2pcl with these contents:

Set the permissions and make it executable:

PostScript™ input sent to this script will be rendered and converted to PCL before being sent on to the printer.

Modify /etc/printcap to use this new input filter:

Test the filter by sending a small PostScript™ program to it:

A filter that detects the type of input and automatically converts it to the correct format for the printer can be very convenient. The first two characters of a PostScript™ file are usually %!. A filter can detect those two characters. PostScript™ files can be sent on to a PostScript™ printer unchanged. Text files can be converted to PostScript™ with Enscript as shown earlier. Create /usr/local/libexec/psif with these contents:

Set the permissions and make it executable:

Modify /etc/printcap to use this new input filter:

Test the filter by printing PostScript™ and plain text files.

lpq(1) shows the status of a user’s print jobs. Print jobs from other users are not shown.

Show the current user’s pending jobs on a single printer:

Show the current user’s pending jobs on all printers:

lprm(1) is used to remove print jobs. Normal users are only allowed to remove their own jobs. root can remove any or all jobs.

Remove all pending jobs from a printer:

Remove a single job from a printer. lpq(1) is used to find the job number.

lpc(8) is used to check and modify printer status. lpc is followed by a command and an optional printer name. all can be used instead of a specific printer name, and the command will be applied to all printers. Normal users can view status with lpc(8). Only root can use commands which modify printer status.

Show the status of all printers:

Prevent a printer from accepting new jobs, then begin accepting new jobs again:

Stop printing, but continue to accept new jobs. Then begin printing again:

Restart a printer after some error condition:

Turn the print queue off and disable printing, with a message to explain the problem to users:

Re-enable a printer that is down:

See lpc(8) for more commands and options.

The printer name is set in the first line of the entry in /etc/printcap. Additional names, or aliases, can be added after that name. Aliases are separated from the name and each other by vertical bars:

Aliases can be used in place of the printer name. For example, users in the Sales department print to their printer with

Users in the Repairs department print to their printer with

All of the documents print on that single printer. When the Sales department grows enough to need their own printer, the alias can be removed from the shared printer entry and used as the name of a new printer. Users in both departments continue to use the same commands, but the Sales documents are sent to the new printer.

It can be difficult for users to locate their documents in the stack of pages produced by a busy shared printer. Header pages were created to solve this problem. A header page with the user name and document name is printed before each print job. These pages are also sometimes called banner or separator pages.

Enabling header pages differs depending on whether the printer is connected directly to the computer with a USB, parallel, or serial cable, or is connected remotely over a network.

Header pages on directly-connected printers are enabled by removing the :sh:\ (Suppress Header) line from the entry in /etc/printcap. These header pages only use line feed characters for new lines. Some printers will need the /usr/shared/examples/printing/hpif filter to prevent stairstepped text. The filter configures PCL printers to print both carriage returns and line feeds when a line feed is received.

Header pages for network printers must be configured on the printer itself. Header page entries in /etc/printcap are ignored. Settings are usually available from the printer front panel or a configuration web page accessible with a web browser.