When you send a print job to the printer daemon, such as printing a text file from Emacs or printing an image from GIMP, the print job is added to the print spool queue. The print spool queue is a list of print jobs that have been sent to the printer and information about each print request, such as the status of the request, the job number, and more.

During the printing process, the Printer Status icon appears in the Notification Area on the panel. To check the status of a print job, click the Printer Status, which displays a window similar to Figure 21.18, “GNOME Print Status”.

To cancel, hold, release, reprint or authenticate a print job, select the job in the GNOME Print Status and on the Job menu, click the respective command.

To view the list of print jobs in the print spool from a shell prompt, type the command lpstat -o. The last few lines look similar to the following:

$ lpstat -o
Charlie-60              twaugh            1024   Tue 08 Feb 2011 16:42:11 GMT
Aaron-61                twaugh            1024   Tue 08 Feb 2011 16:42:44 GMT
Ben-62                  root              1024   Tue 08 Feb 2011 16:45:42 GMT

If you want to cancel a print job, find the job number of the request with the command lpstat -o and then use the command cancel job number. For example, cancel 60 would cancel the print job in Example 21.11, “Example of lpstat -o output”. You can not cancel print jobs that were started by other users with the cancel command. However, you can enforce deletion of such job by issuing the cancel -U root job_number command. To prevent such canceling change the printer operation policy to Authenticated to force root authentication.

You can also print a file directly from a shell prompt. For example, the command lp sample.txt prints the text file sample.txt. The print filter determines what type of file it is and converts it into a format the printer can understand.