CUPS also supports the use of “interface scripts” as known from System V AT&T printing systems. These are often used for PCL printers, from applications that generate PCL print jobs. Interface scripts are specific to printer models. They have a role similar to PPDs for PostScript printers. Interface scripts may inject the Escape sequences as required into the print data stream if the user, for example, selects a certain paper tray, or changes paper orientation, or uses A3 paper. Interface scripts are practically unknown in the Linux realm. On HP-UX platforms they are more often used. You can use any working interface script on CUPS too. Just install the printer with the -i option:

root# 

lpadmin -p pclprinter -v socket://11.12.13.14:9100 \
          -i /path/to/interface-script

Interface scripts might be the “unknown animal” to many. However, with CUPS they provide the easiest way to plug in your own custom-written filtering script or program into one specific print queue (some information about the traditional use of interface scripts is found at https://playground.sun.com/printing/documentation/interface.html).