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 standard output.
When grops is run by groff options can be passed to grops using the groff -P option. 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. The default value can be specified by a broken n command in the DESC file. Otherwise the default value is 0.