How can I filter an array of json objects using jq?

Question

I have been able to get this far.

json input, 'data.json':

[
  {
    "Selected": null,
    "Family Name": "Jones",
    "Couple Name": "Jones, Adam & Rachael Margaret",
    "Family Phone": "404-4477",
    "Family Email": "[email protected]",
    "Family Address": "777 Aggies Court Kindly, California 95388 ",
    "Head Of House Name": "Jones, Adam",
    "Head Of House Phone": "(583) 404-2488",
    "Head Of House Email": "[email protected]",
    "Spouse Name": "Jones, Rachael Margaret",
    "Spouse Phone": null,
    "Spouse Email": null,
    "Child Name": null,
    "Child Phone": null,
    "Child Email": null
  },
  {
    "Selected": "x",
    "Family Name": "Xiong",
    "Couple Name": "Xiong, Arlene Frances",
    "Family Phone": null,
    "Family Email": null,
    "Family Address": "888 Walnut Ave. Blatant, California 95388 ",
    "Head Of House Name": "Xiong, Arlene Frances",
    "Head Of House Phone": "583-500-7917",
    "Head Of House Email": "[email protected]",
    "Spouse Name": null,
    "Spouse Phone": null,
    "Spouse Email": null,
    "Child Name": null,
    "Child Phone": null,
    "Child Email": null
  },
  {
    "Selected": "x",
    "Family Name": "Blair",
    "Couple Name": "Blair, Toby & Silvia",
    "Family Phone": "358-4645",
    "Family Email": null,
    "Family Address": "333 Cindy St. Stoic, California 95388 ",
    "Head Of House Name": "Blair, Toby",
    "Head Of House Phone": null,
    "Head Of House Email": "[email protected]",
    "Spouse Name": "Blair, Silvia",
    "Spouse Phone": null,
    "Spouse Email": null,
    "Child Name": null,
    "Child Phone": null,
    "Child Email": null
  }
]

I can use this to filter:

cat data.json | jq '.[] | select(.Selected != null) | {"Head Of House Name", "Head Of House Phone", "Head Of House Email", "Family Phone", "Family Email"}'

The results:

{
  "Head Of House Name": "Xiong, Arlene Frances",
  "Head Of House Phone": "583-500-7917",
  "Head Of House Email": "[email protected]",
  "Family Phone": null,
  "Family Email": null
}
{
  "Head Of House Name": "Blair, Toby",
  "Head Of House Phone": null,
  "Head Of House Email": "[email protected]",
  "Family Phone": "358-4645",
  "Family Email": null
}

Notice there are no array brackets around the array of objects and no comma between the objects... indicating the result is not an array.

The problem is that the result is not an array of objects (frankly, I'm not sure what it is). How can I start with an array of json objects, filter them and end up with a filtered list of objects?

Answer 1

When you use the filter .[], you are actually breaking the array result into separate results for each of the items. What you're seeing in the end is each of the individual results, one after the other.

To ensure they are kept as an array, you can put the results back into an array by wrapping your filter with square brackets:

[
    .[] |
    select(.Selected != null) |
    {
        "Head Of House Name",
        "Head Of House Phone",
        "Head Of House Email",
        "Family Phone",
        "Family Email"
    }
]

Or keep it as an array by using the map() filter, you could then remove the .[] part:

map(
    select(.Selected != null) |
    {
        "Head Of House Name",
        "Head Of House Phone",
        "Head Of House Email",
        "Family Phone",
        "Family Email"
    }
)

If you asked me, you should stick with map().