Posting XML Data with cURL

cURL is a powerful command-line tool for transferring data with URLs. It’s commonly used for tasks like downloading files, but it’s equally adept at sending data to web servers, including XML payloads. This tutorial will guide you through how to POST XML data to a server using cURL.

Understanding the Basics

Before diving into the commands, let’s clarify the core concepts. An HTTP POST request sends data to a server to create or update a resource. When dealing with XML, the data needs to be formatted correctly and sent with the appropriate headers to indicate the content type.

The cURL Command Structure

The basic cURL command structure for posting XML data is as follows:

curl -X POST -H "Content-Type: application/xml" -d @<xml_file> <url>

Let’s break down each part:

• curl: The command to invoke cURL.
• -X POST: Specifies that you are making a POST request. By default, cURL uses a GET request.
• -H "Content-Type: application/xml": This is a crucial header. It tells the server that the data you’re sending is XML. Without this, the server might misinterpret the data.
• -d @<xml_file>: This is where you specify the XML data. The @ symbol tells cURL to read the data from the specified file. Replace <xml_file> with the actual path to your XML file. Alternatively, you can provide the XML data directly within the command using quotes (see examples below).
• <url>: The URL of the server you are sending the data to.

Example 1: Posting from an XML File

Let’s say you have an XML file named request.xml with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<Transaction>
  <SomeParam1>Some-Param-01</SomeParam1>
  <Password>SomePassW0rd</Password>
  <Transaction_Type>00</Transaction_Type>
</Transaction>

To POST this file to http://localhost:8080, you would use the following command:

curl -X POST -H "Content-Type: application/xml" -d @request.xml http://localhost:8080

Example 2: Posting XML Data Directly in the Command

You can also embed the XML data directly within the command. This is useful for simple XML structures or testing purposes.

curl -X POST -H "Content-Type: application/xml" -d '<?xml version="1.0" encoding="UTF-8"?><Transaction><SomeParam1>Some-Param-01</SomeParam1></Transaction>' http://localhost:8080

Important Considerations:

• Content-Type Header: Always include the Content-Type: application/xml header. The server relies on this header to correctly process the XML data.
• File Paths: Ensure the file path to your XML file is correct. Incorrect paths will result in errors.
• Quotes: When embedding XML directly in the command, use appropriate quotes (single or double) to enclose the XML data. Be mindful of escaping special characters within the XML if necessary.
• Escaping: If your XML contains characters that have special meaning in the shell (like $, \, or '), you’ll need to escape them properly to prevent unintended interpretation by the shell.
• Server Configuration: Make sure the server you’re posting to is configured to accept POST requests and process XML data.

By following these instructions, you can effectively post XML data to a server using cURL from the command line. This is a versatile technique for integrating with web services, sending data to APIs, and automating various tasks.