Join an array to create JSON dynamically

Question

Declaring JSON in bash is kind of annoying because you have to escape a lot of characters.

Say I have an array like this:

 value1="foo"
 value2="bar"
 arr=("key1" "$value1" "key2" "$value2")

Is there a way to somehow join the array with ":" and "," characters.

The only thing I can think of is a loop where you add the right characters, something like this:

data="";

for i in "${arr[@]}"; do
    data="$data\"$i\""
done

Solution 1

With jo, which makes it easy to generate JSON on the command line:

$ jo -p key1="$value1" key2="$value2"
{
   "key1": "foo",
   "key2": "bar"
}

or, depending on what you want the end result to be,

$ jo -a -p "$(jo key1="$value1")" "$(jo key2="$value2")"
[
   {
      "key1": "foo"
   },
   {
      "key2": "bar"
   }
]

Note that jo will also properly encode the values in the strings $value1 and $value2.

Solution 2

With perl:

$ perl -MJSON -e 'print JSON->new->pretty(1)->encode({@ARGV})' -- "${arr[@]}"
{
   "key2" : "bar",
   "key1" : "foo"
}