Using jq to update objects within a JSON document if the value corresponding to a given key starts with a specified string

Question

I have the given JSON and want to change the id value of all elements, which starts with test in the name element:

{
    "other-value": "some-id",
    "values": [
        {
            "name": "test-2017-12-01",
            "id": "1"

        },
        {
            "name": "othert",
            "id": "2"
        }

    ]
}

The following jq commands works jqplay

jq (.values[] | select(.name == "test-afs").id) |= "NEWID"

But when I try it with startswith it stops working, what am I missing? jqplay

(.values[] | select(.name | startswith("test")).id) |= "NEWID" 

jq: error (at :14): Invalid path expression near attempt to access element "id" of {"name":"test-afs","id":"id"} exit status 5

Answer 1

You can also use map, like this:

jq '(.values)|=(map((if .name|startswith("test") then .id="NEWID"  else . end)))' file

Output:

{
  "other-value": "some-id",
  "values": [
    {
      "name": "test-2017-12-01",
      "id": "NEWID"
    },
    {
      "name": "othert",
      "id": "2"
    }
  ]
}

Answer 2

Please note that since the release of jq 1.5, jq has been enhanced to support the query that previously failed. For example, using the current 'master' version:

jq -c '(.values[] | select(.name | startswith("test")).id) |= "NEWID"'
{"other-value":"some-id","values":[{"name":"test-2017-12-01","id":"NEWID"},{"name":"othert","id":"2"}]}

Using earlier versions of jq, if/then/else/end can be used in this type of situation as follows:

.values[] |= if .name | startswith("test") then .id = "NEWID" else . end

If using map, a minimalist expression would be:

.values |= map(if .name|startswith("test") then .id = "NEWID" else . end)