Find the value of key from JSON

Question

I'd like to extract the "id" key from this single line of JSON.

I believe this can be accomplished with grep, but I am not sure on the correct way.

If there is a better way that does not have dependencies, I would be interested.

Here is my example output:

{
  "data": {
    "name": "test",
    "id": "4dCYd4W9i6gHQHvd",
    "domains": ["www.test.domain.com", "test.domain.com"],
    "serverid": "bbBdbbHF8PajW221",
    "ssl": null,
    "runtime": "php5.6",
    "sysuserid": "4gm4K3lUerbSPfxz",
    "datecreated": 1474597357
  },
  "actionid": "WXVAAHQDCSILMYTV"
}

Answer 1

If you have a grep that can do Perl compatible regular expressions (PCRE):

$ grep -Po '"id": *\K"[^"]*"' infile.json
"4dCYd4W9i6gHQHvd"

• -P enables PCRE
• -o retains nothing but the match
• "id": * matches "id" and an arbitrary amount of spaces
• \K throws away everything to its left ("variable size positive look-behind")
• "[^"]*" matches two quotes and all the non-quotes between them

If your grep can't do that, you an use

$ grep -o '"id": *"[^"]*"' infile.json | grep -o '"[^"]*"$'
"4dCYd4W9i6gHQHvd"

This uses grep twice. The result of the first command is "id": "4dCYd4W9i6gHQHvd"; the second command removes everything but a pair of quotes and the non-quotes between them, anchored at the end of the string ($).

But, as pointed out, you shouldn't use grep for this, but a tool that can parse JSON – for example jq:

$ jq '.data.id' infile.json
"4dCYd4W9i6gHQHvd"

This is just a simple filter for the id key in the data object. To get rid of the double quotes, you can use the -r ("raw output") option:

$ jq -r '.data.id' infile.json
4dCYd4W9i6gHQHvd

jq can also neatly pretty print your JSON:

$ jq . infile.json
{
  "data": {
    "name": "test",
    "id": "4dCYd4W9i6gHQHvd",
    "domains": [
      "www.test.domain.com",
      "test.domain.com"
    ],
    "serverid": "bbBdbbHF8PajW221",
    "ssl": null,
    "runtime": "php5.6",
    "sysuserid": "4gm4K3lUerbSPfxz",
    "datecreated": 1474597357
  },
  "actionid": "WXVAAHQDCSILMYTV"
}

Answer 2

Just pipe your data to jq and select by keys

"data": {
    "name": "test",
    "id": "4dCYd4W9i6gHQHvd",
    "domains": [
      "www.test.domain.com",
      "test.domain.com"
    ],
    "serverid": "bbBdbbHF8PajW221",
    "ssl": null,
    "runtime": "php5.6",
    "sysuserid": "4gm4K3lUerbSPfxz",
    "datecreated": 1474597357
  },
  "actionid": "WXVAAHQDCSILMYTV"
} | jq '.data.id'     

# 4dCYd4W9i6gHQHvd

Tutorial Here