json-diff

A lot of tools diff json, but only json-diff’s output is easily processable by a program.

In this post, we’ll explore json-diff (a tool from my json-toolkit), how to use it and how to write programs that use its output.

Using json-diff

json-diff is an easy-to-use CLI tool. It takes only two arguments: FILE1 and FILE2 which are json files.

Sample usage

$ echo '{"k": "v"}' > kv.json
$ echo '{"k": "o"}' > ko.json
$ json-diff kv.json ko.json
[{"leftValue":"v","path":["k"],"rightValue":"o"}]

We can also pretty print the output by piping the output to jq.

$ json-diff kv.json ko.json | jq
[
  {
    "leftValue": "o",
    "path": [
      "k"
    ],
    "rightValue": "v"
  }
]

json-diff doesn’t have a pretty printing option built in because jq does that for us.

Explanation of the output

The json-diff output is an array of “difference objects”. Each difference object has a:

• path (required) -j path is an array of strings and numbers that describe where in the json the difference lies. Strings are for access…