There are several existing tools to check the ink level of your printer.
Let’s take two of them : ink and inkblot
Install them :
root@localhost:~# apt-get install ink inkblot
ink is a command-line tool whereas inkblot is an ink level monitor with a GUI.
Please verify that your printer is currently supported :
If your printer belongs to the list of the supported ones, you have to add read access to the device
which stands for your printer :
root@localhost~# chmod o+r /dev/usb/lp0
As a non-root user, to check the ink level :
fool@localhost:~$ ink -p usb
Here is the kind of result you could expect :
ink v0.5.0 (c) 2009 Markus Heinz
hp deskjet 5550
If you launch inkblot from your Gnome menu, then a icon will appear in your tray icon.
By left-clicking on it, you will get the status of your ink level within a pop-up.
More info : man ink
Nota Bene : make sure that your printer is correctly plugged and switched on.