Running Linux, 5th Edition - Matthias Kalle Dalheimer [271]
If you specify the -Z option with enscript, it attempts to detect PostScript files passed to it and passes them through unaltered.
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Warning
If a PostScript file is passed to enscript and is interpreted as a text file (probably because enscript was not called with the -Z option), enscript will encapsulate it and pass it through to print. This can result in the PostScript code being printed out literally. Even a small PostScript file can use up a lot of paper in this way.
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Note that you could specify the default print queue to use either in PRINTER or as a -P argument stored to the ENSCRIPT environment variable. If you set ENSCRIPT to specify a queue to use, that queue will be used every time enscript filters one of your files. We recommend that you set PRINTER rather than -P in ENSCRIPT so that you can change the queue specification and have it filtered appropriately.
Printing Using GUI Tools
Most GUI programs use the standard printing tools, such as lpr, behind the scenes. These programs display friendly print dialog boxes, such as the one shown in Figure 14-1 (for OpenOffice). Typically, you select your printer from the list near the top (called Name in Figure 14-1). You can also set various program-specific options, such as the number of pages to print and the number of copies. When you've set your options, click a button to begin printing, such as the OK button in Figure 14-1.
Figure 14-1. GUI programs present dialog boxes that serve as interfaces to more traditional tools
Frequently, there's little you can do to adjust the way a GUI program prints; there are no options that enable you to tell it to use a variant printing command, so you're stuck with whatever options the program provides. Other times, though, the program does present such options. One way to do this that's quite obvious is to present a print dialog box that enables you to enter the print command. For instance, Figure 14-2 shows the xv print dialog box. Rather than select a printer from a drop-down list, you enter the print command, including any printer specification, just as you would at a command prompt.
A few programs combine these two approaches, providing both a drop-down list of printers and a way to specify the print command. Some programs also provide configuration options that enable you to set the printing command you want to use. Such options, if present, are usually accessible from the program's preferences or configuration dialog box. Consult your program's documentation if you want to change the way it prints.
Figure 14-2. Some GUI programs enable you to specify a print command to suit your needs
How the Printing System Processes a File
Generally, after you have handed your document or file that you want printed over to the printing system, you can forget about it until the printed sheet comes out of the printer. But when things go wrong and the sheet does not appear, or if you are simply curious (like us!), you might want to know what goes on behind the scenes between the lpr command and the output tray of your printer. If you want, you can skip this section and come back here later.
Only the root user has the ability to access printers directly, without using the printing system. (That's not a wise thing to do, by the way.) Linux doesn't grant system users the ability to address various physical devices directly because crippling conflicts could result, and also because it's just too much work for them. Instead, utilities call background system processes to schedule your printing. Among other tasks, these processes convert source file data to print to a specific printer using its printer language and protocols, set the print resolution, format the pages, and add (or know not to add) header and footer data and page numbering.