javascript - Concatenating millions of xml files in a single json file using bash -

i merge 2.5 million smallish xml files directory tree 1 large json file, , trying using bash using find , xml2json utility.

i'm pretty new bash , haven't done complicated it. intuition following (but long way working):

find . -exec xml2json {} ; cat >> merged.json 

problem #1: can't figure out how use xml2json utility -exec.

find . -exec /usr/bin/xml2json < {}  

doesn't work (seems it's waiting more input?). neither

find . -exec /usr/bin/xml2json {} 

how working?

problem #2: efficient way concatenate files? using cat isn't going create well-formed json file, can concatenate in brackets @ start , end , commas in between? or should use jq's -s? need stream or parallelize it?

if turns out bash bad this, efficient alternatives in javascript, r, or python useful. thanks.