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How to merge 2 json files using jq (deep merge and concat array)

With jq command, I want to merge multiple json files.

But I have no idea how to achieve below expectation.

thanks in advance

a.json

{
    "key1": {
        "key2": [
            1,
            2
        ]
    },
    "key3": "aaa"
}

b.json

{
    "key1": {
        "key2": [
            3,
            4,
            5
        ]
    },
    "key4": "bbb"
}

expected result

{
    "key1": {
        "key2": [
            1,
            2,
            3,
            4,
            5
        ]
    },
    "key3": "aaa",
    "key4": "bbb"
}
Tags:

2

Answers


  1. 0

    jq -s 'reduce .[] as $item ({}; . + ($item | with_entries(if .key == "key1" then .value = (.value + $item.key1) else . end)))' a.json b.json

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  2. 0

    The problem is, that you want to merge like * would, but treat colliding arrays like + would. You could prepare those arrays such that merging with * will eventually work as desired, e.g. by pre-processing the addition, and storing it in the last affected array.

    # Use with option `jq -s` so that the inputs are collected into an array
reduce (
  # Find highest ranked arrays
  [paths(arrays) | select(all(.[1:][]; type == "string"))]
  # Group those that would collide
  | group_by(.[1:])[]
) as $group (.;
  # Store the addition into the last of those arrays
  setpath($group[-1]; [getpath($group[])] | add)
)
# Perform the actual merge (for only two inputs, `first * last` would suffice)
| reduce .[1:][] as $next (first; . * $next)

    {
  "key1": {
    "key2": [
      1,
      2,
      3,
      4,
      5
    ]
  },
  "key3": "aaa",
  "key4": "bbb"
}

    Demo

    Alternatively, use another JSON processor that provides such merging techniques. For example, mikefarah/yq implements a *+ operator that "merges objects, but appends arrays". Note that yq is primarily a YAML processor (so the manual is focused around YAML examples) but it can also handle JSON input/output (if not clear from the filename extensions, use the explicit -pj -oj flags).

    yq '. *+ load("b.json")' a.json
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