Cups Backends - To stdin or to not stdin?

Michael Sweet mike at
Mon Aug 8 08:14:03 PDT 2005

Anonymous wrote:
> ...
> So, my main question is:
> How does Cups decide which form of invokation it should use to launch
> the backend?
> Or,
> Under what circumstances will the data be passed via stdin, rather
> than via a disk based file?

Your backend will get the filename when there are no filters
involved for the job.  Typically this is for so-called "raw"
printing of printer-ready files, however it is also used when
printing a file to an intelligent server which will do additional
processing on the file.

Normally a backend reads from stdin since one or more filters will
be used to convert the job file into something the printer can
handle and add any printer-specific options (duplexing, paper tray
selection, etc.)

That said, I highly recommend that you conform to the CUPS backend
interface and support both methods.  It is not hard, and will ensure
that your backend works properly in all situations.

Michael Sweet, Easy Software Products           mike at easysw dot com
Internet Printing and Document Software

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