You might not need 'jq' for simpler use cases

April 8, 2022

I wanted to find out how other people use the AZURE_CONFIG_DIR environment variable¹ and I came across a rather ingenious way² to not rely on JQ for working with JSON in simpler use cases in the process, namely:

jq() {
    echo -n "$1" | python3 -c "import json, sys; print(json.load(sys.stdin)${2})"
}

$ jq "$(cat ~/.azure/azureProfile.json)" "['subscriptions'][0]['name']"
tst002

This is wholly unnecessary when working Azure CLI as that already has the --query option for defining a JMESPath query, but could still be useful nonetheless in more constrained environments.

I’ve recently been using the command line interface of ‘json’ as well as it can very easily do simple things like indenting:

$ python -m json.tool --indent 2 < file.json
[
  {
    "username": "john.doe",
    "id": 1,
    "last_name": "Doe",
    "name": "John"
  },
  {
    "username": "ben.smith",
    "id": 2,
    "last_name": "Smith",
    "name": "John"
  }
]

And sorting:

$ python -m json.tool --sort-keys < file.json
[
    {
        "id": 1,
        "last_name": "Doe",
        "name": "John",
        "username": "john.doe"
    },
    {
        "id": 2,
        "last_name": "Smith",
        "name": "John",
        "username": "ben.smith"
    }
]

And validating:

$ echo '[{"id": 1, username: "john.doe"}]' | python -m json.tool
Expecting property name enclosed in double quotes: line 1 column 12 (char 11)

Consider this example from Skopeo’s README (I’ve shortened the target image from registry.fedoraproject.org/fedora:latest to image to avoid horizontal scrolling):

$ skopeo inspect --config docker://image  | jq
{
  "created": "2022-12-09T05:50:20Z",
  "architecture": "amd64",
  "os": "linux",
  "config": {
    "Env": [
      "DISTTAG=f37container",
      "FGC=f37",
      "container=oci"
    ],
    "Cmd": [
      "/bin/bash"
    ],
    "Labels": {
      "license": "MIT",
      "name": "fedora",
      "vendor": "Fedora Project",
      "version": "37"
    }
  },
  "rootfs": {
    "type": "layers",
    "diff_ids": [
      "sha256:ab03326cd6b0316148039cc3533a48126b41675046011565f840e042caab0cbf"
    ]
  },
  "history": [
    {
      "created": "2022-12-09T05:50:20Z",
      "comment": "Created by Image Factory"
    }
  ]
}

This is equivalent to:

$ skopeo inspect --config docker://image | python -m json.tool --indent 2
{
  "created": "2022-12-09T05:50:20Z",
  "architecture": "amd64",
  "os": "linux",
  "config": {
    "Env": [
      "DISTTAG=f37container",
      "FGC=f37",
      "container=oci"
    ],
    "Cmd": [
      "/bin/bash"
    ],
    "Labels": {
      "license": "MIT",
      "name": "fedora",
      "vendor": "Fedora Project",
      "version": "37"
    }
  },
  "rootfs": {
    "type": "layers",
    "diff_ids": [
      "sha256:ab03326cd6b0316148039cc3533a48126b41675046011565f840e042caab0cbf"
    ]
  },
  "history": [
    {
      "created": "2022-12-09T05:50:20Z",
      "comment": "Created by Image Factory"
    }
  ]
}

The only thing that might be different for you is that the output of jq might be highlighted accordingly, but that might not be worth the extra dependency for you, though yes there is more typing if you aren’t one to alias such long-ish incantations.

Here’s another one:

$ skopeo inspect docker://image | jq -r '.Digest'
sha256:ce08a91085403ecbc637eb2a96bd3554d75537871a12a14030b89243501050f2

The exact same value can be grabbed with:

$ skopeo inspect docker://image | python3 -c "import json, sys; print(json.load(sys.stdin)['Digest'])"
sha256:ce08a91085403ecbc637eb2a96bd3554d75537871a12a14030b89243501050f2

If you are comfortable with Python, then any further manipulations are very accessible as well. All in all I’d say pure Python should at least be given a chance if your use cases are this trivial.