$ groff --help
usage: groff [-abceghijklpstvzCEGNRSUVXZ] [-dcs] [-ffam] [-mname] [-nnum]
[-olist] [-rcn] [-wname] [-Darg] [-Fdir] [-Idir] [-Karg] [-Larg]
[-Mdir] [-Parg] [-Tdev] [-Wname] [files...]
-h print this message
-v print version number
-e preprocess with eqn
-g preprocess with grn
-j preprocess with chem
-k preprocess with preconv
-p preprocess with pic
-s preprocess with soelim
-t preprocess with tbl
-G preprocess with grap
-J preprocess with gideal
-R preprocess with refer
-a produce ASCII description of output
-b print backtraces with errors or warnings
-c disable color output
-dcs define a string c as s
-ffam use fam as the default font family
-i read standard input after named input files
-l spool the output
-mname read macros tmac.name
-nnum number first page n
-olist output only pages in list
-rcn define a number register c as n
-wname enable warning name
-z suppress formatted output
-C enable compatibility mode
-Darg use arg as default input encoding. Implies -k
-E inhibit all errors
-Fdir search dir for device directories
-Idir search dir for soelim, troff, and grops. Implies -s
-Karg use arg as input encoding. Implies -k
-Larg pass arg to the spooler
-Mdir search dir for macro files
-N don't allow newlines within eqn delimiters
-Parg pass arg to the postprocessor
-S enable safer mode (the default)
-Tdev use device dev
-U enable unsafe mode
-V print commands on stdout instead of running them
-Wname inhibit warning name
-X use X11 previewer rather than usual postprocessor
-Z don't postprocess