How To Use Multiline JSON In A Curl Command?

Using Here Documents for Multiline JSON

Here Documents let you include multiline JSON in curl commands. This method keeps the JSON structure without escaping characters.

To use a Here Document in your curl command:

1. Start your curl command as usual.
2. Use the --data-binary @- option to tell curl to read data from stdin.
3. Add << EOF after the curl command.
4. Insert your JSON data on new lines.
5. End the JSON data with EOF on a new line.

Example:

curl -X POST http://www.example.com/api/users \
-H "Content-Type: application/json" \
--data-binary @- << EOF
{
    "field1": "test",
    "field2": {
        "foo": "bar"
    }
}
EOF

NAME="John Doe"
AGE=30

curl -X POST http://www.example.com/api/users \
-H "Content-Type: application/json" \
--data-binary @- << EOF
{
    "name": "$NAME",
    "age": $AGE,
    "active": true
}
EOF

Escaping Newlines in JSON Payloads

You can also include multiline JSON in curl commands by escaping newlines. This works well for shorter JSON payloads.

To escape newlines:

1. Replace each newline with \n.
2. Enclose the JSON payload in single quotes.

Example:

curl -X POST http://www.example.com/api/users \
-H "Content-Type: application/json" \
-d '{"field1": "test",\n"field2": {\n    "foo": "bar"\n}}'

Using a Separate JSON File

For larger JSON payloads, you can store the data in a separate file and reference it in the curl command.

To use this method:

1. Create a JSON file (e.g., payload.json) with your data.
2. Use the @ symbol followed by the filename in your curl command.

Example:

Create a file named payload.json:

{
    "field1": "test",
    "field2": {
        "foo": "bar"
    }
}

Then use this curl command:

curl -X POST http://www.example.com/api/users \
-H "Content-Type: application/json" \
-d @payload.json

This method keeps your JSON data separate from the curl command, making it easier to manage and update.