jq

Filtering

Considering we have sample.json:

cat <<EOT | jq '.items[] | select(.key == "one")'
{
  "items": [
    {
      "key": "one",
      "value": "value for one"
    },
    {
      "key": "two",
      "value": "value for two"
    }
  ]
}
EOT

evaluates to:

{
  "key": "one",
  "value": "one value"
}

Piping

This is how the following pipeline looks:

• Select items

• Select one

• Filter out nulls

• Get the first element from values : .values | .[0] or simply .values[0]

cat <<EOT | jq '.items[] | .one | select(. != null) | .values[0]'
{
  "items": [
    {
      "one": {
        "values": ["a", "b"]
      }
    },
    {
      "two": {
        "values": ["c", "d"]
      }
    }
  ]
}
EOT

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• Tag: shell