AG6HQ AG6HQ - 3 months ago 23
JSON Question

Update one JSON file values with values from another JSON using JQ

So I have two JSON files:

bosh.json:


{
"key_pair_name": "my-aws-keypair",
"ssh_private_key": "my-key-name",
"trusted_certificates": "my-trusted-certs"
}


model.json:


{
"trusted_certificates": "vault-supplied-value",
"vm_password_type": "generate"
}


and I want to update the model.json file with the bosh.json file so it looks like this:

{
"trusted_certificates": "my-trusted-certs",
"vm_password_type": "generate"
}


I tried this:

jq --argfile bosh bosh.json '. += $bosh' model.json


but I get too many keys

{
"trusted_certificates": "my-trusted-certs",
"vm_password_type": "generate",
"key_pair_name": "my-aws-keypair",
"ssh_private_key": "my-key-name"
}


and

jq --argfile bosh bosh.json '. + $bosh' model.json


yeilds the same...

{
"trusted_certificates": "my-trusted-certs",
"vm_password_type": "generate",
"key_pair_name": "my-aws-keypair",
"ssh_private_key": "my-key-name"
}


while this

jq --argfile bosh bosh.json '. = $bosh' model.json


yields the incorrect keys...

{
"key_pair_name": "my-aws-keypair",
"ssh_private_key": "my-key-name",
"trusted_certificates": "my-trusted-certs"
}


Does anyone have any ideas how to get the expected results using jq?
by the way, I cannot use the value of the key for the updates, as i will have unexpected results in other permutations...

Answer Source

The requirements are not completely clear, but here's the solution to one interpretation. This solution can easily be modified to match the other obvious interpretation.

Assuming the file bosh.jq contains the following jq program:

reduce keys[] as $k (.; if $bosh|has($k) then .[$k] = $bosh[$k] else . end)

then the command:

jq --argfile bosh bosh.json -f bosh.jq model.json

will in effect emit the edited version of model.json.

Using with_entries

If you prefer a reduce-free approach, consider:

with_entries(.key as $k | if $bosh|has($k) then .value = $bosh[$k] else . end )

Note that if $bosh|has($k) ... is NOT the same as if $bosh[$k] ....