mjhjmtu

I'm using Bash to run the following script snippet on a Linux box.

JSON file contents: [ "id": 123456, "firstName": "John", "lastName": "Smith", "email": "user@domain.com" ]

The JSON file is stored in the $data[0] array which is piped into the Bash script.

Bash script:

trafficEmployeeId=123456
cat "$data[0]" | jq --arg employeeId $trafficEmployeeId '. | select(.id == $employeeId) | .firstName'

And the output from the script should be John. But I get nothing.

Even if you assigned shell variable trafficEmployeeId with a number it will be passed into jq script as a string argument.
The solution is to parse the argument as a number with jq's tonumber function.

The second moment is that data[0] contains the array with only one object, so it's enough to access it directly with .[0] and apply simple if operator condition.

Complete solution:

trafficEmployeeId=123456
echo "$data[0]" | jq --arg employeeId "$trafficEmployeeId" '.[0] 
 | if .id == ($employeeId | tonumber) then .firstName else empty end'

The output:

"John"