Escape JSON in Mix shell echo command

Question

I have a similar code to this. I want it to echo a valid JSON with quotes on properties so that it can be piped to another command. But while echoing, it is ripping off all the quotes.

def test_function() do
  map = %{
    "key1" => 12,
    "key2" => "value1",
  }

  json = Poison.encode!(map)
  IO.inspect(json)

  Mix.Shell.cmd(
    "echo #{json}",
    fn x -> IO.puts(x) end
  )
end

Expected

{"key2":"value1","key1":12}

Actual

{key2:value1,key1:12}

Answer 1

I had to quote JSON string in single-quotes

Mix.Shell.cmd(
  "echo '#{json}'",
  fn x -> IO.puts(x) end
)

Ref

Answer 2

You shouldn't need to rely on the OS echo command when Elixir IO already ties into STDOUT. I think you may be getting into trouble here because you are sending the result of IO.inspect AND the result of IO.puts (wrapped in the system's echo command) to STDOUT, so it's doubling things up and at a minimum, this is confusing, but it probably is invalid as well.

This works for me, given a simple github.json file containing

{
    "sha": "d25341478381063d1c76e81b3a52e0592a7c997f",
    "commit": {
        "author": {
            "name": "Stephen Dolan",
            "email": "[email protected]",
            "date": "2013-06-22T16:30:59Z"
        }
    },
    "url": "https://api.github.com/repos/stedolan/jq/commits/d25341478381063d1c76e81b3a52e0592a7c997f"
}

stored alongside a parse.exs script with the following:

contents = File.read!("github.json")
map = Jason.decode!(contents)

json_str = Jason.encode!(map)
IO.puts(json_str)

This decoding and encoding is demonstrates that this is working (substitute Poison or whatever as desired).

Now, I can run the following command via mix run parse.exs and I see the expected result. I can also pipe the output as expected, e.g. to jq:

❯ mix run parse.exs | jq '.sha'
"d25341478381063d1c76e81b3a52e0592a7c997f"