Some examples of the use of gen are:
gen -v amazon
Generate a parser for the grammar amazon.gra, and be
verbose. If the generated parser amazon is up to date, no new
parser is generated. The parser uses a compressed lexicon consisting
of amazon.lex, amazon.pdf, and amazon.cfr. If
these files are not present, they will be generated from the lexical
database amazon.dat for which the interface is defined in
amazon.def.
gen -fc fib
Enforce the generation of a new parser for the grammar fib.gra,
showing certain statistical counters after each parsing.
gen -fp iceleaf
Enforce the generation of a parser for the grammar iceleaf.gra
and let the generated parser create a profile of the grammar.