#!/bin/bash
mk_json_object(){
   local items rest

   printf -v items '  "%s": "%s"' $(json_quote "$1" "$2")
   shift 2
   [ $# -gt 1 ] && printf -v rest ',\n  "%s": "%s"' $(json_quote "$@")
   printf "{\n%s\n}\n" "$items$rest"
}

mk_json_lst(){
   local list rest
   printf -v list '  "%s"' $(json_quote "$1")
   shift
   [ $# -gt 0 ] && printf -v rest ',\n  "%s"' $(json_quote "$@")
   printf "[\n%s\n]\n" "$list$rest"
}

json_quote() {
    while [ $# -gt 0 ]
    do
        val=${1//\\/\\\\}
        val=${val//\"/\\\"}
        val=${val//$'\n'/\\\n}
        val=${val//$'\t'/\\\t}
        val=${val//$'\r'/\\\r}
        val=${val//$'\f'/\\\f}
        val=${val//$'\b'/\\\b}
        printf "%s" "$val"
        shift
        [ $# -gt 0 ] && printf " "
    done
}

mk_json_object_one_val() {
        local key=$1
        while [ $# -gt 1 ]
        do
            shift
            args=( "${args[@]}" "$key" "$1" )
        done
        mk_json_object "${args[@]}"
}

mk_json_object_one_val '$(uname)' "key
1" '"test"' more$'\r'
mk_json_lst test$'\b' key-2

{
  "$(uname)": "key\n1",
  "$(uname)": "\"test\"",
  "$(uname)": "more\r"
}
[
  "test\b",
  "key-2"
]

1:sendmany
2:
3:{"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX":0.01,"1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz":0.02}
4:1
5:
6:["1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX","1353tsE8YMTA4EuV7dgUXGjNFf9KpVvKHz"]