Lists the paths of the input JSON.
The input can either be the json file given as argument $JSON_FILENAME.
If no argument is given, standard input is used.

For this input JSON data:
{ "a": ["x","y"],
  "b": {
       "c": 1
       }
}

the returned paths are:
a.0
a.1
b.c

Note: OpenFoodFacts require to strip the first element of each path and sort/uniq the paths.
The command to run for that is:
cat off.json | allpaths |innerpaths|uniqpaths