sebastiandaschner blog

I’m using the command line a lot and jq is a helpful tool for dealing with JSON data. You can access JSON object properties and array elements by concatenating the property names with dots and square brackets:

$> cat ~/.docker/config.json

{
    "auths": {
        "https://index.docker.io/v1/": {
            "auth": "aBcDeFghiJKlMn="
        },
        [...]
    }
}

$> cat .docker/config.json | jq .

{
  "auths": {
    "https://index.docker.io/v1/": {
      "auth": "aBcDeFghiJKlMn="
    },
    [...]
  }
}

$> cat .docker/config.json | jq .auths
{
  "https://index.docker.io/v1/": {
    "auth": "aBcDeFghiJKlMn="
  },
  [...]
}

You can also access and escape “non-trivial” field names in different ways. You can get the encoded Docker auth authentication as follows, by using square brackets and quotes to escape the property name:

$> cat .docker/config.json | jq '.auths["https://index.docker.io/v1/";].auth'
"aBcDeFghiJKlMn="

$> cat .docker/config.json | jq -r '.auths["https://index.docker.io/v1/";].auth'
aBcDeFghiJKlMn=

You’ll notice the formatted and colorized output of jq. Have a look at the documentation.

Parts of the content of this post were reposted from my newsletter issue 038.

 

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