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How To Use Curl Command In Postman

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Understanding the Power of cURL in Postman

Postman is a beloved tool in the API testing world, but sometimes, you need the raw power of the command line. This is where cURL comes in. cURL is a versatile command-line tool for transferring data using various protocols. Integrating cURL with Postman unlocks a whole new level of flexibility and control for your API testing.

1. Sending Simple GET Requests with cURL

Let’s start with the basics: sending a GET request to fetch data from an API. Here’s a step-by-step guide:

  1. Open Postman: Launch Postman and create a new request.
  2. Select the GET method: Choose “GET” as the HTTP method.
  3. Enter the URL: In the request URL field, type the API endpoint you want to access. For example: https://api.example.com/users.
  4. Add Authorization (if needed): If the API requires authentication, use the “Authorization” tab in Postman to provide your credentials.
  5. Send the request: Click the “Send” button.
  6. Copy the cURL command: In Postman’s “Code” tab, select “cURL” from the dropdown. You’ll find the generated cURL command representing the request you just sent.

Sample Code:

Terminal window
curl --location --request GET 'https://api.example.com/users' \
--header 'Authorization: Bearer your_access_token'

2. Executing POST Requests with cURL in Postman

For creating or updating data, you’ll need to send POST requests. Here’s how cURL handles them:

  1. Configure the POST request in Postman: Follow the same steps as for GET requests, but choose “POST” as the method.
  2. Define the request body: In the “Body” tab of your Postman request, specify the data you want to send to the server. You can choose between JSON, form-data, or raw text.
  3. Generate the cURL equivalent: In the Postman “Code” tab, select “cURL” to obtain the command.

Sample Code:

Terminal window
curl --location --request POST 'https://api.example.com/users' \
--header 'Authorization: Bearer your_access_token' \
--header 'Content-Type: application/json' \
--data-raw '{
    "name": "John Doe",
    "email": "john.doe@example.com"
}'

3. Utilizing Headers and Parameters with cURL

Many APIs require passing headers or query parameters to control request behavior. cURL shines in handling these:

Headers:

  • Postman: Add headers directly to the “Headers” section of your request.
  • cURL: Use the --header flag for each header, like --header 'Content-Type: application/json'.

Parameters:

  • Postman: Add query parameters in the request URL itself.
  • cURL: Include them directly in the URL using the format https://api.example.com/users?page=2&limit=10.

Sample Code:

Terminal window
curl --location --request GET 'https://api.example.com/users?page=2&limit=10' \
--header 'Authorization: Bearer your_access_token' \
--header 'Accept: application/json'

4. Working with Files and Uploads using cURL

cURL simplifies file uploads with the --upload-file flag.

  1. Postman: Select “form-data” in the “Body” tab, adding the file as a key-value pair.
  2. cURL: Use the --upload-file option to specify the local file path.

Sample Code:

Terminal window
curl --location --request POST 'https://api.example.com/upload' \
--header 'Authorization: Bearer your_access_token' \
--header 'Content-Type: multipart/form-data' \
--form 'file=@/path/to/your/file.jpg'

5. Understanding cURL Flags and Options

cURL offers many flags and options for customization. Here are a few common ones:

  • -X, —request: Specifies the HTTP method (GET, POST, PUT, DELETE, etc.).
  • -H, —header: Adds custom headers to the request.
  • —data, —data-raw: Provides the request body data.
  • -d, —data-urlencode: Encodes data as URL-encoded strings.
  • -u, —user: Sets basic authentication credentials.
  • -k, —insecure: Ignores SSL certificate validation (use with caution).
  • —verbose: Provides detailed output, including response headers and body.
  • —output: Saves the response to a file.

Example with Multiple Flags:

Terminal window
curl -v -X POST --header 'Content-Type: application/json' \
--data-raw '{ "name": "Jane Doe", "email": "jane.doe@example.com" }' \
https://api.example.com/users  --output response.txt

Additional Tips

  • Postman’s “Code” Tab: Always use the “Code” tab in Postman to generate the cURL equivalent of your requests. It saves time and ensures accuracy.
  • Experiment and Learn: Don’t be afraid to experiment with cURL flags and options. The more you use it, the better you’ll understand its power.
  • Use Shell Scripting: For complex or repetitive API testing scenarios, leverage shell scripting to automate cURL commands.

By combining the intuitive graphical interface of Postman with the raw power of cURL, you can elevate your API testing to a whole new level of control and flexibility.

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