usage: /usr/bin/troff [-abcCEiRSUz] [-d ctext] [-d string=text] [-f font-family] [-F font-directory] [-I inclusion-directory] [-m macro-package] [-M macro-directory] [-n page-number] [-o page-list] [-r cnumeric-expression] [-r register=numeric-expression] [-T output-device] [-w warning-category] [-W warning-category] [file ...]
usage: /usr/bin/troff {-v | --version}
usage: /usr/bin/troff --help

GNU troff transforms groff(7) language input into the device-
independent page description language detailed in groff_out(5); it
is the heart of the GNU roff document formatting system.  Many
people prefer to use the groff(1) command, a front end that also
runs preprocessors and output drivers in the appropriate order and
with appropriate options.  See the troff(1) manual page.