What is Curl?
Curl is a popular command-line tool that allows you to send requests to the server, upload files, and submit web forms. Curl supports over 25+ protocols, including HTTP, HTTPS, SFTP, FTP, and has built-in support for web forms, SSL, user authentication, and HTTP cookies. Curl works on Linux, Windows, and Mac.
What is HTTP POST request method?
HTTP POST is one of 9 common HTTP request methods supported by HTTP. The HTTP POST method allows clients to send and servers to receive and process the data contained in the body of a POST message. Sending data in the body of a POST message is optional; some POST requests may not have content in the body, such as requests that only want to update the status of an entity in the database. The POST method is often used for submitting login and contact forms to the server and uploading files and images. The HTTP POST method is used for CRUD operations to create or update a resource on the server. POST requests may change the state of the server and are not idempotent.
How to send a POST request using Curl?
You can send a POST request with Curl by explicitly specifying the POST method with the -X POST command line parameter or passing data to Curl using the -d or --data command line parameter. If you pass data using the -d command-line switch and do not explicitly specify the HTTP method with the -X command-line option, Curl will automatically select the HTTP POST method for the request.
Curl POST Request Syntax
The following is a Curl command to create a POST request with a message body:
- -X: the parameter specifies which HTTP request method will be used when communicating with the server
- -H: the content-type header indicates the data type in the request body
- -d: the parameter specifies the data to be sent to the server in the POST message body
The -X parameter specifies which HTTP request method will be used when communicating with the server. The -d parameter specifies the data to be sent to the server in the body of the POST message. The content-type header indicates the data type in the request body.
Curl POST Request Examples
The following are examples of sending a Curl POST request with a detailed description:
Posting a request body using Curl
To post data on the body of a request message using Curl, you must use the -d or --data command line parameter. The Content-Type header specifies the data type in the message body. The server will use this header to interpret and process the received data.
Posting JSON data using Curl
If you want to post JSON data with Curl, you need to set the Content-Type to application/json and use the -d parameter to pass JSON to the Curl. The command line parameter -H "Content-Type: application/json" sets the JSON content type. JSON data is passed as a string.
Posting form data using Curl
If you want to post form data with Curl, you can use the -F (--form) or -d (--data) command-line parameters. With the -F command-line parameter, form data is sent as "multipart/form-data", and with the -d command-line parameter, form data is sent as "application/x-www-form-urlencoded".
Posting a file using Curl
If you want to post a file with Curl, add the -d and -F command-line options and start the data with the @ symbol. Following the @ symbol, you must specify the file path. By default, Curl provides the Content-Type header based on the file extension, but you can provide a custom Content-Type header using the -H command-line option.
Posting XML using Curl
To post XML data to the server using Curl, you can pass the XML with the -d command line option and specify the data type in the body of the message with the -H Content-Type: application/xml option.
Sending basic auth credentials with Curl POST request
You can pass Basic Authentication credentials to Curl using the --user="login: password" command-line option. Curl automatically encrypts the user's credentials into a base64 encoded string and passes them to the server using the Authorization: Basic [token] header.