Normally grops should be invoked by using the groff command with a - Tps option. If no files are given, grops will read the standard input. A filename of - will also cause grops to read the standard input.
PostScript output is written to the stan- dard output.
When grops is run by groff options can be passed to grops using the groff - P option. Normally grops produces output that conforms the Document Struc- turing Conventions version 3.0. Unfortunately some spoolers and previewers can't handle such output. The value of n controls what grops does to its output acceptable to such programs. A value of 0 will cause grops not to employ any workarounds.