This content originally appeared on DEV Community and was authored by Peter Meszaros
From time to time there is requirement build JSON object at bash script. This can be done in several ways. Depend on complexity of requirement.
As first attemption came up to write exact JSON to variable, something like this
#!/usr/bin/env bash
JSON=$(cat <<-END
{
"what":"something",
"when":"now"
}
END
)
echo "$JSON"
As result this JSON is produced
{
"what": "something",
"when": "now"
}
Next attempt is add key values from variables
#!/usr/bin/env bash
WHAT="something"
WHEN="now"
JSON=$(jq -n \
--arg what "$WHAT" \
--arg when "$WHEN" \
'$ARGS.named'
)
echo "$JSON"
Here is used jq for JSON built.
--arg name value passes values predefined variables. Value is available as $name.
All named arguments are also available as $ARGS.named Because the format of $ARGS.named is already an object, jq can output it as is.
This is usable when JSON structure is fixed and known. But JSON can be variable, depend on usage. What if there some variable missing or next variable has to be added. Some more flexibility can be welcomed.
Here is approach how to create JSON progressively
#!/usr/bin/env bash
JSON=$(jq -n '')
WHAT="something"
if [[ -n "$WHAT" ]]; then
JSON=$(echo $JSON | jq --arg what "${WHAT}" '. += $ARGS.named')
fi
if [[ -n "$WHEN" ]]; then
JSON=$(echo $JSON | jq --arg what "${WHAT}" '. += $ARGS.named')
fi
echo "$JSON"
At beginning, with JSON=$(jq -n '') empty JSON is created.
Then variables are assigned.
Next condition is crucial for JSON built.
if [[ -n "$WHAT" ]]; then
JSON=$(echo $JSON | jq --arg what "${WHAT}" '. += $ARGS.named')
fi
If variable is set and not null, will be added to JSON.
With this technique, JSON creation in bash script can be so flexible.
This content originally appeared on DEV Community and was authored by Peter Meszaros
Peter Meszaros | Sciencx (2023-05-16T14:10:53+00:00) JQ – build JSON at bash script. Retrieved from https://www.scien.cx/2023/05/16/jq-build-json-at-bash-script/
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