Stuctured logs in shell script using JQ - json

Question

I've been wanting to logs some shells scripts to a file to be picked up by an agent like Fluentbit and shipped off to Cloudwatch and Datadog.
I found this example on the web which works like a charm using jq.
__timestamp(){
date "+%Y%m%dT%H%M%S"
}
__log(){
log_level="$1"
message="$2"
echo '{}' | jq \
--arg timestamp "$(__timestamp)"
--arg log_level "$log_level" \
--arg message "$message" \
'.timestamp=$timestamp|.log_level=$log_level|.message=$message' >> logs.log
}
__log "INFO" "Hello, World!"
The one issue is that the output is rendering a full json with newlines and tabs. Easy on the eyes, but not great for cloud logging services.
{
"timestamp": "20220203T162320",
"log_level": "INFO",
"message": "Hello, World!"
}
How would I modify to render the output on one line like so?
{"timestamp": "20220203T171908","log_level": "INFO","message": "Hello, World!"}

Answer 1

Use the --compact-output or -c option: jq -c --arg … '…' >> logs.log
From the manual:
--compact-output / -c:
By default, jq pretty-prints JSON output. Using this option will
result in more compact output by instead putting each JSON object
on a single line.
After having read your linked article about "Structured Logging", this is how I would have implemented said __log function:
__log(){
jq -Mcn --arg log_level "$1" --arg message "$2" \
'{timestamp: now|todate, $log_level, $message}'
}
__log "INFO" "Hello, World!"

Answer 2

🤦 Somehow I completely missed Step 3.0 The Finishing Touches of this terrific guide which answers my question perfectly.
In case anyone else was curious, the solution is here:
__timestamp(){
date "+%Y%m%dT%H%M%S"
}
__log(){
log_level="$1"
message="$2"
echo '{}' | \
jq --monochrome-output \
--compact-output \
--raw-output \
--arg timestamp "$(__timestamp)" \
--arg log_level "$log_level" \
--arg message "$message" \
'.timestamp=$timestamp|.log_level=$log_level|.message=$message'
}
__log "INFO" "Hello, World!"
Which outputs:
{"timestamp":"20210812T191730","log_level":"INFO","message":"Hello, World!"}