如何剖析 CUPS 作业控制文件“/var/spool/cups/cNNNNNN”？

Question

When printing a job to a CUPS server, you can set up the cupsd.conf parameters PreserveJobHistory and PreserveJobFiles to control how many jobs you want to keep.

CUPS always temporarily stores the actual print job files in directory /var/spool/cups/ . The spool files as submitted by the print client (before CUPS' conversion chain of filters kicks in) are always named dNNNNNN-001 (starting with a 'd' as in 'datafile') where NNNNNN is the job ID assigned by CUPS. If you submit a multi-document print job, the second document's spool file within the same job ID is named dNNNNNN-002 , and so on...

Also, the same directory will hold files starting with another character, the control files and they will be named cNNNNNN for each job.

I want to dissect these control files files.

When I use the strings tool, it only reveals part of what I want to get at:

Example:

 sudo strings /var/spool/cups/d00089

  attributes-charset
  utf-8H
  attributes-natural-language
  en-us
  printer-uri
  %ipp://localhost:631/printers/hp2B
  job-originating-user-name
  kurtpfeifleB
  job-name
  hosts!
  copies
  finishings
  job-cancel-after
  job-hold-until
  no-hold!

  job-priority
  job-sheets
  noneB
  none!
  number-up
  job-uuid
  -urn:uuid:ca854775-f721-34a5-57e0-b38b8fb0f4c8B
  job-originating-host-name
  localhost!
  time-at-creation
  time-at-processing
  time-at-completed
  job-id
  job-state
  job-state-reasons
  processing-to-stop-point!
  job-media-sheets-completed
  job-printer-uri
  (ipp://host13.local:631/printers/hp!

  job-k-octets
  document-format
  text/plainA
  job-printer-state-message
  job-printer-state-reasons
  none

Also, that strings output doesn't look very nice.

Question: Is there a programmatic (or other) way to dissect these CUPS job control files and get at their complete content with all included info?

Answer 1

Found an answer myself...

When you compile CUPS from sources, there is the subdirectory cups . It also holds a Makefile specific to this subdir. That Makefile contains a build target named "unittests" which is NOT built by default!

But if you run make unittests it not only runs its unit tests, but also creates a few command line utilities which potentially can be put to quite some good use outside of unit tests too!

For the case to solve my problem, it turns out that the testipp CLI utility is pure gold. See yourself:

sudo ./testipp /var/spool/cups/c00089

 operation-attributes-tag:

     attributes-charset (charset): utf-8
     attributes-natural-language (naturalLanguage): en-us

 job-attributes-tag:

     printer-uri (uri): ipp://localhost:631/printers/hp
     job-originating-user-name (nameWithoutLanguage): kurtpfeifle
     job-name (nameWithoutLanguage): hosts
     copies (integer): 1
     finishings (enum): none
     job-cancel-after (integer): 10800
     job-hold-until (keyword): no-hold
     job-priority (integer): 50
     job-sheets (1setOf nameWithoutLanguage): none,none
     number-up (integer): 1
     job-uuid (uri): urn:uuid:ca854775-f721-34a5-57e0-b38b8fb0f4c8
     job-originating-host-name (nameWithoutLanguage): localhost
     time-at-creation (integer): 1472022731
     time-at-processing (integer): 1472022731
     time-at-completed (integer): 1472022732
     job-id (integer): 89
     job-state (enum): completed
     job-state-reasons (keyword): processing-to-stop-point
     job-media-sheets-completed (integer): 0
     job-printer-uri (uri): ipp://host13.local:631/printers/hp
     job-k-octets (integer): 1
     document-format (mimeMediaType): text/plain
     job-printer-state-message (textWithoutLanguage): Printing page 1, 4% complete.
     job-printer-state-reasons (keyword): none

Unfortunately, running make install will not install this tool into the system, and thusly it never gets exposed to any CUPS administrator! Also, Linux distro packagers may easily overlook it. testipp runs under the radar for most CUPS geeks.

There are a few more useful utilities built by make unittests :
These are: testadmin, testarray, testcache, testclient, testconflicts, testcreds, testcups, testdest, testfile, testgetdests, testhttp, testi18n, testlang, testoptions, testppd, testpwg, testraster, testsnmp .

Unfortunately, no Linux distro currently builds and ships these useful tools. So if you know a distro packager, please point him to this discovery here and ask her to package a nice bundle for all end-users of cups-test-utils.rpm , or cups-test-utils.deb or cups-test-utils.tgz or whatever the package name suffixes for his $distro are! `

Answer 2

I had a similar issue - we needed the duration of jobs and discovered your thread. testIPP worked fine so far, but I didn't want to compile cups just for these little neat tool and also I need it to integrate in other go based applications.

I've started to implement small CLI util in go which also can be used as library https://github.com/ui-kreinhard/go-cups-control-files