?????: LPD applet

walter harms WHarms at bfs.de
Mon Feb 25 10:45:33 UTC 2008



Vladimir Dronnikov wrote:
> Hi, Walter!
> 
> 1. Let us discuss spool format.
> 2. Let us decide whether to support all these banner pages, mailing
> features, ...
> 3. Let us decide whether to delegate "actual" printing to a helper
> application or just dump data file to a device or a file.
> 
> My draft proposal is:
> 1. Spool can be similar to Maildir: incoming jobs are dumped to tmp,
> then are moved atomically to new. A special thread (or process) then
> spawned which moves pending job from new to cur and prerforms "actual"
> printing.

no problem with that as long it is configurable. E.g. our system has
64mb for everything (most is eaten by data) but is capable of using a
usb-stick. For a few euros you get gigabytes.
I have no idea why you want a thread. the mail analogy is fine. you need
one "dispatcher" and a "deliverer" for each queue. and you are ready.

The "deliverer" can make all the filtering popen(" cat myfile | myfilter -o myoptions | cat >mydevice");
an interesting question is "can we/you explore similarities from the mailsystem"
(we have a sendmail and i never took a look into it)


the tricky job is to implement priority, changes of etc. we can drop it.


> 
> 2. Not for now. Printing to laser printers differs dramatically from
> printing to line printers. To make LPD smart enough to produce pages
> by itself is
> IMHO just a bloat for now.
> 
do not think to much about it, when we do not need a backchannel it is easy.
lpd should not produce pages other than the header page.

> 3. Helpers rule: we can have pre, print, post scripts that can perform
> all smart capabilities (banners, mail notification,  etc.) of #2. If a
> print script is absent we can just dump datafile to the device. Yes,
> this may be way tricky but the power and flexibility of such an
> approach deserves tricks inventions :)
> 


mail is simple and can be done via popen(). it is the only way the system can
inform the user about an aborted job.


re,
 wh


> --
> Vladimir
> 
> 
> 2008/2/25, walter harms <WHarms at bfs.de>:
>>
>> dronnikov at gmail.com wrote:
>>> Hi!
>>>
>>> Cosmetic changes to lpr.
>>>
>>> New applet: tiny lpd. Seems to be working with lp[rq] applets :)
>>> Needs to be tested on real printing device and I do not have any...
>>>
>>> Need feedback, people!
>>> Do we want any queueing?
>>> Do we need some pre- and postprocessing, preferably via external helpers?
>>>
>>> --
>>> Vladimir
>>>
>> Hi Vladimir,
>> just give me some more time.
>>
>> an because you ask: i would like to see some spooling daemon.
>> 1. there are non-spooling lpd daemons out there.
>> 2. spooling is a good solution for bad lines to prevent data loss
>>
>> btw: you do not need a printing device any decent ld lets you print to a
>> file
>> please be aware that implementing filter can be tricky.
>>
>>
>>
>> re,
>>  wh
>>
> 
> 
> 



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