[printing-discuss] Re: [Inkjet-list] Device capabilities?

Michael Sweet mike at easysw.com
Thu Apr 4 05:45:19 PST 2002

luke.kendall at cisra.canon.com.au wrote:
> ...
> I don't understand, I think.  I'm imagining you have 6 printers, all the
> same model, all plugged in via USB.  Does the file name get a number
> appended, or something, to distinguish each one?

Each queue is named, e.g. "CanonS600"; if you have multiple printers,
then you may choose to add a number on the end, e.g. CanonS600_1234,
however the name refers to a specific printer and does not change.

> If so, and a user unplugs printer 3, do 4, 5, and 6 get re-numbered?
> It sounds tricky.

No, the printer name does not change.


The underlying devices (in Linux, anyways) might be renumbered when a
printer is added or removed, however that is a separate issue for the
CUPS device daemon to manage, and isn't something that the user or
printer driver needs to worry about.

 > ...
>> If you use the CUPS API library, I think you will be able to handle
>> the PPD files without root permissions.
> Sorry, I still don't understand.  Unless the files in /etc/cups/ppd are
> publically writable?

They are not publicly writable, however your printer driver process
(started by the CUPS scheduler) will have write access to the files
since it is running as the owner of those files.

(and CUPS tells you which PPD file to look at)

> If they're not, and I'm not the owner, or in the group, then a library
> function can't give me write permission, I thought.  I thought that
> required a setuid or setgid process to be involved.

No; if you don't have local access, you can always use HTTP to
access and update the files as long as you can provide the correct
authentication info (admin username + password in the default

Michael Sweet, Easy Software Products                  mike at easysw.com
Printing Software for UNIX                       http://www.easysw.com

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