jq read .txt file and write the values to json file - json

Question

I want to use jq to parse a .txt file with a list of country codes and write them to the value in a JSON object.
Here is what I have so far:
cat myfile.json |
jq -R -f test_id.txt 'select(.country == []).country = "test_id.txt"' > newfile.json
Where .txt file looks like this:
"NSC"
"KZC"
"KCC"
"KZL"
"NZG"
"VRU"
"ESM"
"KZF"
"SFU"
"EWF"
"KQY"
"KQV"
and my JSON looks like this:
{
"scsRequestId": null,
"includeMetadata": true,
"includeHoldings": true,
"country": [],
"region": [],
"oclcSymbol": []
}
Here is the error I am getting:
jq: error: syntax error, unexpected QQSTRING_START, expecting $end (Unix shell quoting issues?) at <top-level>, line 2:
"KZC"
jq: 1 compile error
I want the list of country codes to go into the country array.

Answer 1

-f's argument is the file to read the filter to run from. If you want to read data from a file, that's a use for --slurpfile, not -f.
Thus:
jq --slurpfile countries test_id.txt '.country=$countries' <myfile.json >newfile.json
When run with your provided inputs, the resulting contents in newfile.json are:
{
"scsRequestId": null,
"includeMetadata": true,
"includeHoldings": true,
"country": [
"NSC",
"KZC",
"KCC",
"KZL",
"NZG",
"VRU",
"ESM",
"KZF",
"SFU",
"EWF",
"KQY",
"KQV"
],
"region": [],
"oclcSymbol": []
}