DOKK / manpages / debian 10 / gron / gron.1.en
GRON(1) User Commands GRON(1)

gron - transform JSON into discrete, greppable assignments

gron [OPTIONS] [FILE|URL]

gron –-version

gron –-help

gron transforms JSON into discrete assignments to make it easier to grep for what you want and see the absolute `path' to it. It eases the exploration of APIs that return large blobs of JSON but have terrible documentation.

reverse the operation (turn assignments back into JSON)
colorize output (default on tty)
monochrome (don't colorize output)
treat each line of input as a separate JSON object
disable certificate validation
represent gron data as JSON stream
don't sort output (faster)

Get JSON from a file:

$ gron testdata/two.json 
json = {};
json.contact = {};
json.contact.email = "mail@tomnomnom.com";
json.contact.twitter = "@TomNomNom";
json.github = "https://github.com/tomnomnom/";
json.likes = [];
json.likes[0] = "code";
json.likes[1] = "cheese";
json.likes[2] = "meat";
json.name = "Tom";

From a URL:

$ gron http://headers.jsontest.com/
json = {};
json.Host = "headers.jsontest.com";
json["User-Agent"] = "gron/0.1";
json["X-Cloud-Trace-Context"] = "6917a823919477919dbc1523584ba25d/11970839830843610056";

Or from STDIN:

$ curl -s http://headers.jsontest.com/ | gron
json = {};
json.Accept = "*/*";
json.Host = "headers.jsontest.com";
json["User-Agent"] = "curl/7.43.0";
json["X-Cloud-Trace-Context"] = "c70f7bf26661c67d0b9f2cde6f295319/13941186890243645147";

Grep for something and easily see the path to it:

$ gron testdata/two.json | grep twitter
json.contact.twitter = "@TomNomNom";

gron makes diffing JSON easy too:

$ diff <(gron two.json) <(gron two-b.json)
3c3
< json.contact.email = "mail@tomnomnom.com";
---
> json.contact.email = "contact@tomnomnom.com";

The output of gron is valid JavaScript:

$ gron testdata/two.json > tmp.js
$ echo "console.log(json);" >> tmp.js
$ nodejs tmp.js
{ contact: { email: 'mail@tomnomnom.com', twitter: '@TomNomNom' },
  github: 'https://github.com/tomnomnom/',
  likes: [ 'code', 'cheese', 'meat' ],
  name: 'Tom' }

It's also possible to obtain the gron output as JSON stream via the --json switch:

$ curl -s http://headers.jsontest.com/ | gron --json
[[],{}]
[["Accept"],"*/*"]
[["Host"],"headers.jsontest.com"]
[["User-Agent"],"curl/7.43.0"]
[["X-Cloud-Trace-Context"],"c70f7bf26661c67d0b9f2cde6f295319/13941186890243645147"]

gron can also turn its output back into JSON:

$ gron testdata/two.json | gron -u
{
  "contact": {
    "email": "mail@tomnomnom.com",
    "twitter": "@TomNomNom"
  },
  "github": "https://github.com/tomnomnom/",
  "likes": [
    "code",
    "cheese",
    "meat"
  ],
  "name": "Tom"
}

This means you use can use gron with grep and other tools to modify JSON:

$ gron testdata/two.json | grep likes | gron --ungron
{
  "likes": [
    "code",
    "cheese",
    "meat"
  ]
}

or

$ gron --json testdata/two.json | grep likes | gron  --json --ungron
{
  "likes": [
    "code",
    "cheese",
    "meat"
  ]
}

To preserve array keys, arrays are padded with null when values are missing:

$ gron testdata/two.json | grep likes | grep -v cheese
json.likes = [];
json.likes[0] = "code";
json.likes[2] = "meat";
▶ gron testdata/two.json | grep likes | grep -v cheese | gron --ungron
{
  "likes": [
    "code",
    null,
    "meat"
  ]
}

Although gron's primary purpose is API discovery, when combined with other tools like grep it can do some interesting things.

As an exercise, let's try to mimic some of the examples from the jq tutorial (https://stedolan.github.io/jq/tutorial/).

Disclaimer: munging data on the command line with gron can be useful, but using tools like grep and sed to manipulate the data is error-prone and shouldn't be relied on in scripts.

Get the last 5 commits from the gron repo:

$ gron "https://api.github.com/repos/tomnomnom/gron/commits?per_page=5"
json = [];
json[0] = {};
json[0].author = {};
json[0].author.avatar_url = "https://avatars.githubusercontent.com/u/58276?v=3";
json[0].author.events_url = "https://api.github.com/users/tomnomnom/events{/privacy}";
...
json[4].parents[0].html_url = "https://github.com/tomnomnom/gron/commit/cbcad2299e55c28a9922776e58b2a0b5a0f05016";
json[4].parents[0].sha = "cbcad2299e55c28a9922776e58b2a0b5a0f05016";
json[4].parents[0].url = "https://api.github.com/repos/tomnomnom/gron/commits/cbcad2299e55c28a9922776e58b2a0b5a0f05016";
json[4].sha = "91b204972e63a1166c9d148fbbfd839f8697f91b";
json[4].url = "https://api.github.com/repos/tomnomnom/gron/commits/91b204972e63a1166c9d148fbbfd839f8697f91b";

To make the rest of this a little more readable, let's add an alias for that:

$ alias ggh='gron "https://api.github.com/repos/tomnomnom/gron/commits?per_page=5"'

Extract just the first commit using fgrep "json[0]":

$ ggh | fgrep "json[0]"
json[0] = {};
json[0].author = {};
json[0].author.avatar_url = "https://avatars.githubusercontent.com/u/58276?v=3";
json[0].author.events_url = "https://api.github.com/users/tomnomnom/events{/privacy}";
json[0].author.followers_url = "https://api.github.com/users/tomnomnom/followers";
...
json[0].parents[0].html_url = "https://github.com/tomnomnom/gron/commit/48aba5325ece087ae24ab72684851cbe77ce8311";
json[0].parents[0].sha = "48aba5325ece087ae24ab72684851cbe77ce8311";
json[0].parents[0].url = "https://api.github.com/repos/tomnomnom/gron/commits/48aba5325ece087ae24ab72684851cbe77ce8311";
json[0].sha = "7da81e29c27241c0a5c2e5d083ddebcfcc525908";
json[0].url = "https://api.github.com/repos/tomnomnom/gron/commits/7da81e29c27241c0a5c2e5d083ddebcfcc525908";

Get just the committer's name and the commit message using egrep "(committer.name|commit.message)":

$ ggh | fgrep "json[0]" | egrep "(committer.name|commit.message)"
json[0].commit.committer.name = "Tom Hudson";
json[0].commit.message = "Adds 0.1.7 to changelog";

Turn the result back into JSON using gron --ungron:

▶ ggh | fgrep "json[0]" | egrep "(committer.name|commit.message)" | gron --ungron
[
  {
    "commit": {
      "committer": {
        "name": "Tom Hudson"
      },
      "message": "Adds 0.1.7 to changelog"
    }
  }
]

gron preserves the location of values in the JSON, but you can use sed to remove keys from the path:

$ ggh | fgrep "json[0]" | egrep "(committer.name|commit.message)" | sed -r "s/(commit|committer)\.//g"
json[0].name = "Tom Hudson";
json[0].message = "Adds 0.1.7 to changelog"

With those keys removed, the result is a `flattened' object, which looks much cleaner when turned back into JSON with gron --ungron:

$ ggh | fgrep "json[0]" | egrep "(committer.name|commit.message)" | sed -r "s/(commit|committer)\.//g" | gron --ungron
[
  {
    "message": "Adds 0.1.7 to changelog",
    "name": "Tom Hudson"
  }
]

Removing the fgrep "json[0]" from the pipeline means we do the same for all commits:

$ ggh | egrep "(committer.name|commit.message)" | sed -r "s/(commit|committer)\.//g" | gron --ungron
[
  {
    "message": "Adds 0.1.7 to changelog",
    "name": "Tom Hudson"
  },
  {
    "message": "Refactors natural sort to actualy work + be more readable",
    "name": "Tom Hudson"
  },
...

To include the html_url key for each commit's parents, all we need to do is add parents.*html_url into our call to egrep:

$ ggh | egrep "(committer.name|commit.message|parents.*html_url)" | sed -r "s/(commit|committer)\.//g"
json[0].name = "Tom Hudson";
json[0].message = "Adds 0.1.7 to changelog";
json[0].parents[0].html_url = "https://github.com/tomnomnom/gron/commit/48aba5325ece087ae24ab72684851cbe77ce8311";
json[1].name = "Tom Hudson";
json[1].message = "Refactors natural sort to actualy work + be more readable";
json[1].parents[0].html_url = "https://github.com/tomnomnom/gron/commit/3eca8bf5e07151f077cebf0d942c1fa8bc51e8f2";
...

To make the structure more like that in the final example in the jq tutorial, we can use sed -r "s/\.html_url//" to remove the .html_url part of the path:

▶ ggh | egrep "(committer.name|commit.message|parents.*html_url)" | sed -r "s/(commit|committer)\.//g" | sed -r "s/\.html_url//"
json[0].name = "Tom Hudson";
json[0].message = "Adds 0.1.7 to changelog";
json[0].parents[0] = "https://github.com/tomnomnom/gron/commit/48aba5325ece087ae24ab72684851cbe77ce8311";
json[1].name = "Tom Hudson";
json[1].message = "Refactors natural sort to actualy work + be more readable";
json[1].parents[0] = "https://github.com/tomnomnom/gron/commit/3eca8bf5e07151f077cebf0d942c1fa8bc51e8f2";
...

And, of course, the statements can be turned back into JSON with gron --ungron:

$ ggh | egrep "(committer.name|commit.message|parents.*html_url)" | sed -r "s/(commit|committer)\.//g" | sed -r "s/\.html_url//" | gron --ungron
[
  {
    "message": "Adds 0.1.7 to changelog",
    "name": "Tom Hudson",
    "parents": [
      "https://github.com/tomnomnom/gron/commit/48aba5325ece087ae24ab72684851cbe77ce8311"
    ]
  },
  {
    "message": "Refactors natural sort to actualy work + be more readable",
    "name": "Tom Hudson",
    "parents": [
      "https://github.com/tomnomnom/gron/commit/3eca8bf5e07151f077cebf0d942c1fa8bc51e8f2"
    ]
  },
...

Read from a local file/network:

$ gron /tmp/apiresponse.json
$ gron http://jsonplaceholder.typicode.com/users/1 

Retrieve remote JSON and pipe through gron:

$ curl -s http://jsonplaceholder.typicode.com/users/1 | gron

Flatten and filter JSON through gron, before turning result back into JSON:

$ gron http://jsonplaceholder.typicode.com/users/1 | grep company | gron --ungron

It's recommended that you alias ungron or norg (or both!) to gron --ungron. Put something like this in your shell profile (e.g. in ~/.bashrc):

alias norg="gron --ungron"
alias ungron="gron --ungron"

Or you could create a shell script in your $PATH named `ungron` or `norg` to affect all users: ``` gron --ungron "$@" ```

0 OK

1 Failed to open file

2 Failed to read input

3 Failed to form statements

4 Failed to fetch URL

5 Failed to parse statements

6 Failed to encode JSON

Upstream bug tracker: https://github.com/tomnomnom/gron/issues

Copyright (c) 2016 Tom Hudson

This manual page is based on the gron documentation. It was created by Nick Morrott <knowledgejunkie@gmail.com> for the Debian GNU/Linux system, but may be used by others

grep(1), ack(1), ag(1), rg(1), jq(1)

July 2018 0.6.0