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Printing on UNIX and alikes has a long history. There used to be two rather different approaches: the BSD-style printing and the SystemV-style printing. For compatibility, Linux with CUPS supports the commands from both styles. Also note that lp does not behave exactly like lpr, lpq has somewhat different options than lpstat and lprm is almost, but not quite, like cancel. Which one you use is not important, just pick the commands that you are comfortable with, or that you may know from previous experiences with UNIX-like systems.
8.1.2. Formatting
8.1.2.1. Tools and languages
If we want to get something sensible out of the printer, files should be formatted first. Apart from an abundance of formatting software, Linux comes with the basic UNIX formatting tools and languages.
Modern Linux systems support direct printing, without any formatting by the user, of a range of file types: text, PDF, PostScript and several image formats like PNG, JPEG, BMP and GIF.
For those file formats that do need formatting, Linux comes with a lot of formatting tools, such as the pdf2ps, fax2ps and a2ps commands, that convert other formats to PostScript. These commands can create files that can then be used on other systems that don't have all the conversion tools installed.
Apart from these command line tools there are a lot of graphical word processing programs. Several complete office suites are available, many are free. These do the formatting automatically upon submission of a print job. Just to name a few: OpenOffice.org, KOffice, AbiWord, WordPerfect, etc.
The following are common languages in a printing context:
• groff: GNU version of the UNIX roff command. It is a front-end to the groff document formatting system. Normally it runs the troff command and a post-processor appropriate for the selected device. It allows generation of PostScript files.
• TeX and the macro package LaTeX: one of the most widely used markup languages on UNIX systems. Usually invoked as tex, it formats files and outputs a corresponding device-independent representation of the typeset document.
Technical works are still frequently written in LaTeX because of its support for mathematic formulas, although efforts are being made at W3C (the World Wide Web Consortium) to include this feature in other applications.
• SGML and XML: Free parsers are available for UNIX and Linux. XML is the next generation SGML, it forms the basis for DocBook XML, a document system (this book is written in XML, for instance).
Printing documentation
The man pages contain pre-formatted troff data which has to be formatted before it can roll out of your printer. Printing is done using the -t option to the man command:
man -t command > man-command.ps
Then print the PostScript file. If a default print destination is configured for your system/account, you can just issue the command man -t command to send the formatted page to the printer directly.
8.1.2.2. Previewing formatted files
Anything that you can send to the printer can normally be sent to the screen as well. Depending on the file format, you can use one of these commands:
• PostScript files: with the gv (GhostView) command.
• TeX dvi files: with xdvi, or with KDE's kdvi.