Mastering cURL: How to Check HTTP Status Codes of Websites

The command-line tool curl is widely used for transferring data with URLs, especially in the realms of web development, testing, and automation. Understanding how to effectively use curl to return both the HTTP status code and the response body is crucial for diagnosing issues, automating tests, and interacting with APIs. This article delves into the methods and benefits of retrieving HTTP status codes alongside responses using curl.

Basics of Curl

curl stands for “Client URL” and is a software project providing a library and command-line tool for transferring data using various protocols. It is a powerful tool that can be used to request URLs, upload or download data, and even test APIs.

Why Return HTTP Status Code and Response?

HTTP status codes are essential for understanding the response from a server. They tell you if a request was successful (2xx codes), redirected (3xx codes), resulted in client-side error (4xx codes), or server-side error (5xx codes). When combined with the response body, these codes provide a comprehensive view of how the server is handling your requests.

Curl to Return HTTP Status Code and Response

Basic Curl Request:
A simple curl request looks like this:
```
curl [URL]
```
This command retrieves the content found at the URL.

Displaying HTTP Status Code:
To display the HTTP status code, you can use the -w or --write-out flag. This flag allows you to format the output. For example:
```
curl -w "%{http_code}" [URL] 
```
This command will output the HTTP status code of the response.

Combining Response and Status Code:
To get both the response body and the status code, you can use a command like:
```
curl -o response.txt -w "%{http_code}" [URL]
```
This command saves the response body to response.txt and displays the HTTP status code on the terminal.

Handling Redirects:
If your request involves redirects, you might want to use the -L flag to follow redirects. Combine it with the -w flag to capture the final HTTP status code.
```
curl -L -w "%{http_code}" [URL]
```

Verbose Mode for Detailed Information:
For detailed information including request headers, response headers, and more, use the -v or --verbose flag.
```
curl -v -w "%{http_code}" [URL]
```

Advanced Usage

Storing Response and Status Code in Variables:
For scripting purposes, you may want to store the response body and status code in variables. This can be done using shell script techniques.

Using Curl in Automation and Testing:
curl is a great tool for automated testing of APIs and web services. By checking the status code, scripts can automatically determine if a test passed or failed.

Conclusion

curl is a versatile tool that becomes even more powerful when you know how to use it to retrieve HTTP status codes along with responses. This capability is invaluable for debugging, testing, and interacting with web services. Understanding how to effectively harness this feature of curl can significantly enhance your workflows in web development and system administration.