cURL is a powerful command-line tool for transferring data over various network protocols, including HTTP, HTTPS, FTP, and more. Since POST is a request method of HTTP & HTTPS protocols, cURL makes sending POST requests a one-line command that you can run in your terminal easily.
Find the full article on our website.
First, install cURL if you haven’t installed it already. You can find the installation instructions in our How to Use cURL With Proxy blog post.
The basic syntax for sending a POST request using cURL is as below:
curl -X POST -d "Hello" https://example.com/api
Notice the -X flag followed by POST, it tells cURL to make a request using the HTTP protocol’s POST method, and the -d flag sets request data as Hello and sends it to the website https://example.com/api. The -X flag is the short form of the command line option --request.
Like any HTTP request, POST requests created using cURL can also have custom headers. For specifying the Content-Type header, you’ll have to set it using the header flag.
curl -X POST -H "Content-Type: text/plain" -d "Hello" https://example.com/api
In the above command, there’s an additional -H flag which lets users send custom HTTP request headers via cURL. In this case, by specifying the Content-Type header as text/plain you’re letting the web server know that the request body data is in TEXT format.
It’s also possible to send JSON data in the request body. All you need to do is set the appropriate Content-Type header and pass the JSON data with the -d flag. cURL will make a POST request with the JSON data specified in the argument.
curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' https://example.com/api
If you need a straightforward way to create a JSON code from a cURL command, use this cURL to JSON converter.
Similar to JSON, you can also send XML in the request body. You’ll have to make changes to the request header and set it to application/xml.
curl -X POST -H "Content-Type: application/xml" -d '<?xml version="1.0" encoding="UTF-8"?><root><name>John Doe</name><age>30</age></root>' https://example.com/api
To send a file via cURL POST, you’ll have to use the -F flag. Pay attention to the capitalization of the letter “F”. All of the cURL flags or command line options are case-sensitive.
curl -X POST -F "file=@/path/to/img.png" https://example.com/api/upload
As you can see, the above command is uploading an image file. Right after the -F the file path of the image was given. You can also use multiple -F flags to send multiple files to the server as below:
curl -X POST -F "file=@/path/to/img1.png" -F "file=@/path/to/img2.png" https://example.com/api/upload
You can use the -u flag or the --user option to specify the username & password for basic authentication. cURL will automatically create the Authorization header based on your input.
curl -u username:password https://example.com/login
You’ll have to replace username and password with the actual authentication credentials. Also, don’t forget to replace the example URL with your own.