nochetopgn converst PGN files to JSON or counts games IN PGN file. It is not usefull for studiing or playing chess. It is more usefull for developing chess tools working with PGN. If you are not a developer, you most probably do not need it.
It can also convert PGN file to PGN file, which is used for testing validity of the original PGN file.
How to use
Nochetopgn reads input from standard input. One of the ways how to process
PGN file is to use
cat program and "pipe it" to nochetopgn.
cat file.pgn | nochetopgn --json