Easy Duplex Printing (Shallow Thoughts)

Akkana's Musings on Open Source, Science, and Nature.

Sun, 23 Apr 2006

Easy Duplex Printing

Firefox' print system doesn't know how to print just even or just odd pages of a document, so when I need to print out a web page and want it double sided, I've been doing the Duplex Dance: hover over the printer ready to grab each page as it comes out the front so that I can quickly flip it and feed it back into the top of the printer fast enough that the printer doesn't time out with "Out of Paper".

Of course, more often I just sigh and let it print single sided because that's just way too much hassle. But today is Earth Day, so I decided it was time to find a better solution. The solution, obviously, begins with telling the browser to print to a Postscript file. Then the challenge is to find a way to print only the odd pages of the Postscript file, put the pages back in the printer, then print only the even pages.

First I tried to use mpage, which claims to be able to do this. It looked like this command should do it:

mpage -j 1%2 file.ps | lpr
But it didn't work -- it said it was spooling something to the printer, but nothing ever came out. Upon saving the mpage output to a file, I found that gv couldn't show it, citing postscript errors.

But it turns out there's a much easier way: the CUPS lp program has an option called page-set precisely for this purpose, and it's smart about detecting postscript input. This command did the trick:

lp -o page-set=odd file.ps
Then flip the sheets, insert back into the printer, and repeat with even instead of odd. Lovely!

This is documented in http://localhost:631/help/options.html?QUERY=odd#PAGESET -- and the CUPS in-browser help has a search function that took me right to it, I'm happy to note.

Other programs which may to be able to split postscript files into odd and even pages include psselect and perhaps dviduplex.

With a smarter print dialog (one that allowed specifying a custom print command, like Mozilla's used to) you could even define several custom printers, one that printed even pages and one that printed odd. Alas, Firefox' print dialog doesn't allow such things, or even allow defining extra printers. (The Mozilla bug asking for odd/even printing is bug 35228).

From a quick search of about:config, it looks like you might be able to set up something by hand using the print.printer_CUPS/printername.print_command preference (by default mine was set to lpr ${MOZ_PRINTER_NAME:+'-P'}${MOZ_PRINTER_NAME}) but I notice something even more interesting: two variables called print.printer_CUPS/printername.print_evenpages and print.printer_CUPS/printername.print_oddpages (both set to true by default). Also interesting are plex.0.name and plex.count. Might be an easy way to get duplex printing straight from the browser, after doing a little hand-editing to try and persuade Firefox that there's more than one printer. I'll try it next time I need to print something. (It seems wrong to spend Earth Day printing more pages than I actually need.)

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[ 19:21 Apr 23, 2006    More linux | permalink to this entry ]