JQ - Filtering Out JSON Properties Where Keys Do Not Match Length

[pihish]

I have JSON that looks like:

{
  "18003432343": ....,
  "18005553332": ....,
  "1-3-2025 10:36:41_08941100 AM": ....,
  "1-3-2025 11:36:41_08941100 AM": ....
}

I would like to use JQ to filter out all keys where the key length does not equal to 11. So for the above input, the output should be:

{
  "18003432343": ....,
  "18005553332": ....
}

What is the appropriate JQ command line for this?

[shreechaturvedi]

Use with_entries and filter on .key | length:

jq 'with_entries(select(.key | length == 11))' input.json

What this does:

• with_entries turns the object into an array of {key, value} entries, runs the filter on each, then rebuilds an object
• select(.key | length == 11) keeps only entries whose key string is exactly 11 characters

Example:

$ jq 'with_entries(select(.key | length == 11))' <<'JSON'
{
  "18003432343": 1,
  "18005553332": 2,
  "1-3-2025 10:36:41_08941100 AM": 3
}
JSON

{
  "18003432343": 1,
  "18005553332": 2
}

If you only care about digit keys of length 11, tighten the filter:

jq 'with_entries(select(.key | test("^[0-9]{11}$")))' input.json