COMMAND may be used in place of (or in some cases, in addition to) DEVICE, in order to specify an alternate command or subroutine for processing the print file, which is also known as a "print filter." This can be especially useful when interfacing to non-printer devices such as faxes, email, archival systems, etc., as well as for performing special filtering operations on print files without having to change the application that created them. There are two forms of the command, named according to which system will be doing the processing."

Only one COMMAND can be specified in a single printer init file.