gem install json2csv

json2csv convert data/sample.json

json2csv help

NAME
    json2csv - json2csv 0.0.3

SYNOPSIS
    json2csv [global options] command [command options] [arguments...]

GLOBAL OPTIONS
    --help - Show this message

COMMANDS
    convert - Convert json file
    help    - Shows a list of commands or help for one command
    version - Print version info

json2csv help convert

NAME
    convert - Convert json file

SYNOPSIS
    json2csv [global options] convert [command options]

COMMAND OPTIONS
    -d, --delimiter=arg - (default: ,)
    -r, --root=arg      - (default: none)

cat data/sample.json

{
    "12345": {
        "Firstname": "Joe",
        "Lastname": "Doe",
        "Address": {
            "Street": "#2140 Taylor Street, 94133",
            "City": "San Francisco",
            "Details": {
                "Note": "Pool available"
            }
        }
    },

    "45678": {
        "Firstname": "Jack",
        "Lastname": "Plumber",
        "Address": {
            "Street": "#111 Sutter St, 94104",
            "City": "San Francisco",
            "Details": {
                "Note": "Korean Deli near to main entrance"
            }
        }
    }
}

json2csv convert data/sample.json
Converting data/sample.json

cat data/sample.json.csv

id,Firstname,Lastname,Address.Street,Address.City,Address.Details.Note
12345,Joe,Doe,"#2140 Taylor Street, 94133",San Francisco,Pool available
45678,Jack,Plumber,"#111 Sutter St, 94104",San Francisco,Korean Deli near to main entrance