Lua get data from json array with cURL

Question

I need to make a get request and retrieve data from a json array, but I don't know how to fetch a specific array index and print its value. There doesn't seem to be any information online about it either.

local curl = require("lcurl")

c = curl.easy{
    url = 'http://example.com/api/?key=1234',
    httpheader = {
      "Content-Type: application/json";
    };
    writefunction = io.stderr
  }
  c:perform()
c:close()

This returns

[
    {
        "id": "1",
        "name": "admin"
    }
]

But how can I make it print only the value of name?

Do you found a solution for your task?

Serhii Didanov
– Serhii Didanov

2018-12-18 09:25:53 +00:00
Commented Dec 18, 2018 at 9:25 — Serhii Didanov
– Serhii Didanov, Commented Dec 18, 2018 at 9:25

Egor Skriptunoff · Accepted Answer · 2017-09-08 15:29:38Z

1

You can use some JSON library, for example, this one.

local json = require'json'

local function callback(path, json_type, value, pos, pos_last)
   local elem_path = table.concat(path, '/')  -- element's path
   --print(elem_path, json_type, value, pos, pos_last)
   if elem_path == "1/name" then  -- if current element corresponds to JSON[1].name
      print(value)
   end
end

local JSON_string = [[

[
    {
        "id": "1",
        "name": "admin"
    }
]

]]

json.traverse(JSON_string, callback)

Output:

admin

Another solution (more simple, with full decoding of JSON):

local json = require'json'

local JSON_string = [[

[
    {
        "id": "1",
        "name": "admin"
    }
]

]]

print(json.decode(JSON_string)[1].name)

edited Sep 8, 2017 at 15:29

answered Sep 8, 2017 at 15:24

Egor Skriptunoff

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4 Comments

P. Nick Over a year ago

Thanks for your help. What I don't get though is how I'd store the data from curl in a variable, as in c:perform() prints everything to the console but there doesn't seem to be an option to store that data into a variable?

Egor Skriptunoff Over a year ago

@P.Nick - probably, c:setopt_writefunction(...) may help.

moteus Over a year ago

Easy way t={} c:setopt_writefunction(table.insert, t) And after perform do str = table.concat(t)

Kalib Zen Over a year ago

Please answer specifically to what OP requested (which is how to get from URL). I don't see any related URL in the code.

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