Almost every API shows how to interact with the API using cURL. So before moving on, let’s pause a bit and learn more about cURL.

• Why cURL?
• Try using curl to GET a web page
• Requests and responses include headers too
• Query strings and parameters
• Common curl commands related to REST
• Example curl command curl
• Friendly tool recommendation

Why curl?

One of the advantages of REST APIs is that you can use almost any programming language to call the endpoint. The endpoint is simply a resource located on a web server at a specific path.

Each programming language has a different way of making web calls. Rather than exhausting your energies trying to show how to make web calls in Java, Python, C++, JavaScript, Ruby, and so on, you can just show the call using curl.

curl provides a generic, language-agnostic way to demonstrate HTTP requests and responses. Users can see the format of the request, including any headers and other parameters. Your users can translate this into the specific format for the language they’re using.

Try using curl to GET a web page

As mentioned earlier, one reason REST APIs are so familiar is that REST follows the same model as the web. When you type an http address into a browser address bar, you’re telling the browser to make an HTTP request to a resource on a server. The server returns a response, and your browser converts the response to a more visual display. But you can also see the raw code.

To see an example of how curl retrieves a web resource, open a terminal and type the following:

curl http://example.com

Curl will retrieve the HTML code for the site example.com. The browser’s job is to make that code visually readable. curl shows you what you’re actually retrieving.

Requests and responses include headers too

When you type an address into a website, you see only the body of the response. But actually, there’s more going on behind the scenes. When you make the request, you’re sending a request header that contains information about the request. The response also contains a response header.

1. To see the response header in a curl request, include -i in the curl request:

curl http://example.com -I

The header will be included above the body in the response:

~/projects $ curl http://example.com -I
HTTP/1.1 200 OK
Content-Encoding: gzip
Accept-Ranges: bytes
Cache-Control: max-age=604800
Content-Type: text/html; charset=UTF-8
Date: Tue, 04 Dec 2018 04:35:43 GMT
Etag: "1541025663+gzip"
Expires: Tue, 11 Dec 2018 04:35:43 GMT
Last-Modified: Fri, 09 Aug 2013 23:54:35 GMT
Server: ECS (sjc/4F91)
X-Cache: HIT
Content-Length: 606

1. To limit the response to just the header, use -I:

curl http://example.com -I

The header contains the metadata about the response. All of this information is transferred to the browser when you make a request to a URL in your browser (for example, when you surf to a web page online), but the browser doesn’t show you this information. You can see the header information using the Chrome Developer Tools console by looking on the Network tab.

1. Now let’s specify the method. The GET method (read) is implied by default when no other method is specified, but we’ll make it explicit here with the -X parameter:

curl -X GET http://example.com -I

When you go to a website, you submit the request using the GET HTTP method. There are other HTTP methods you can use when interacting with REST APIs. Here are the common methods used when working with REST endpoints:

Note：GET is used by default with curl requests. If you use curl to make HTTP requests other than GET, you need to specify the HTTP method.

Query strings and parameters

The zip code (zip), app ID (appid), and units (units) parameters were passed to the endpoint using “query strings.” The ? appended to the URL indicates the start of the query string. The query string parameters are the parameters that appear after the ?:

?zip=95050&appid=APIKEY&units=imperial

(In the above code, replace APIKEY with your actual API key.)

After the query string, each parameter is separated from other parameters by the ampersand & symbol. The order of the query string parameters doesn’t matter. The order only matters if the parameters are on the left of the query string (and thus part of the URL itself). Any configurable parts of the endpoint that appear before the query string are called path parameters (we’ll dive into these later).

Common curl commands related to REST

curl has a lot of possible commands, but the following are the most common when working with REST APIs.

Example curl command

Here’s an example curl request that combines some of these commands:

curl -i -H "Accept: application/json" -X POST -d "{status:MIA}" http://personsreport.com/status/person123

The request could also be formatted with line breaks to make it more readable:

curl -i \
     -H "Accept: application/json" \
     -X POST \
     -d "{status:MIA}" \
     http://personsreport.com/status/person123 \

(Line breaks are problematic on Windows, so I don’t recommend formatting curl requests like this.)

The Accept header tells the server that the only format we will accept in the response is JSON.

Friendly tool recommendation

Apidog streamlines API processes with testing, debugging, design, mocking, and documentation tools, offering an intuitive interface for easy API requests.

1.Sign up or download:

2.Import cURL Commands: Access the Apidog import window. Paste cURL commands into the text box for seamless integration.

3.Configure Request parameters: Navigate to the API body. Set the frequency of API headers, body, and other settings.

4.Test and Refine

Apidog is user-friendly, cURL provides richer functionality.