Hacking PostScriptPostScript tricks and hacksDuplex printing

Duplex printing

Some printers have the capability to print on both sides of the paper. You can put instructions in a PostScript file to signal the printer to print that file double-sided. (A printer that is not capable of duplex printing should ignore such instructions.) The clumsy but effective brute force way to do this is to edit the PostScript file manually. If you open a PostScript file in your text editor, you will see that the file starts with some comment lines beginning with percent signs. To make the file print double-sided, you can insert the line 

<< /Duplex true >> setpagedevice

at an appropriate point near the end of the comments. You may need to experiment to determine what an "appropriate point" is. If, after saving the edited PostScript file, you can successfully preview the file with ghostview, then the file should print properly. If, on the other hand, you get a message from ghostview about an interpreter error, then you guessed wrong about where to insert the setpagedevice instruction: try again.

(If for some reason you need to print to an old printer that does not understand Level 2 PostScript, then you can use the PostScript instruction statusdict begin true setduplexmode end as an alternate means to enable duplex printing.)

A related special effect is to print the back of each page upside down. You might want to do this, for instance, if you were going to bind a report along the top edge instead of along the side. A suitable PostScript instruction to turn on duplex printing with alternate pages flipped is the following:

<< /Duplex true /Tumble true >> setpagedevice

Warning. Be cautious in editing PostScript files, and make a backup file before you begin. Since PostScript is an interpreted language, introducing one small error near the beginning can render the entire file useless. In particular, be careful not to change the first line of the file. Often the printer recognizes a file as being PostScript by checking that the first four characters in the file are %!PS. If you change one of these characters, or if you introduce a spurious blank line at the beginning, then your printer may spew out pages and pages of junk.

A more elegant approach to duplex printing of LaTeX files is to instruct dvips to incorporate the setpagedevice command into the PostScript file automatically. To do this on a standard Unix system, create a file containing the single line

<< /Duplex true >> setpagedevice

and save the file under the name duplex. Now the command dvips -h duplex moebius.dvi will create the file moebius.ps with the PostScript command for double-sided printing built in. The advantage of this method is that you do not have to edit the PostScript file by hand.

If you use this second method, then you may need to tell dvips where to find the header file duplex. If you have stored the file duplex in your home directory, but you are executing the command dvips in a subdirectory, then dvips may complain about being unable to find a header file. One solution is to add to the .cshrc file in your home directory a line like


which tells dvips to search for header files first in the current directory, then in the system default location, and then in your home directory. (This is not actually the solution I use currently. My set-up is configured with a private subdirectory where I keep custom files related to LaTeX, and I run the command texhash whenever I add files to that subdirectory.)

If you are printing LaTeX documents double-sided, then you may want to use the twoside document-class option. That is, start your LaTeX source file with something like this:


When the twoside option is in effect, LaTeX will attempt to adjust the margins so that the printed areas on the front and back sides of the paper line up. If you are not satisfied with the alignment produced by the twoside option, then you can use the \setlength command to adjust the parameters \oddsidemargin and \evensidemargin by hand.

logo The Math 696 course pages were last modified April 5, 2005.
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Hacking PostScriptPostScript tricks and hacksDuplex printing