Begin by accessing the SonarCloud API, which allows you to retrieve project data. You will need an account on SonarCloud with the necessary permissions to access the API. Visit the SonarCloud documentation page to understand the API endpoints available for the specific data you want to extract.

Log into your SonarCloud account and navigate to the security settings. Generate a new API token if you don't have one already. This token will be used to authenticate your API requests, allowing secure access to your project data.

Determine the correct API endpoint for the data you need, such as project measures, issues, or quality gates. Construct the URL using the SonarCloud base API URL (`https://sonarcloud.io/api`) followed by the specific endpoint path. Append any necessary query parameters to specify the project or data scope.

Use the `curl` command-line tool to make a request to the SonarCloud API. The request should include the API token for authentication. For example:
```
curl -u YOUR_TOKEN: https://sonarcloud.io/api/project_analyses/search?project=YOUR_PROJECT_KEY
```
Replace `YOUR_TOKEN` and `YOUR_PROJECT_KEY` with your actual API token and project key. This command retrieves the data from SonarCloud in JSON format.

Redirect the output of the `curl` command to a local file to save the JSON data. Modify the command as follows:
```
curl -u YOUR_TOKEN: https://sonarcloud.io/api/project_analyses/search?project=YOUR_PROJECT_KEY -o sonarcloud_data.json
```
This command saves the response to a file named `sonarcloud_data.json` in the current directory.

Open the `sonarcloud_data.json` file in a text editor or JSON viewer to ensure the data has been correctly downloaded and is complete. Check for any errors or partial data that might indicate a problem with the API request or network issues.

Create a script (e.g., a shell script) to automate the data retrieval process, especially if you plan to do this regularly. Include error handling and logging to manage potential issues. For instance:
```bash
#!/bin/bash
curl -u YOUR_TOKEN: https://sonarcloud.io/api/project_analyses/search?project=YOUR_PROJECT_KEY -o sonarcloud_data.json
if [ $? -eq 0 ]; then
echo "Data successfully retrieved and saved to sonarcloud_data.json"
else
echo "Failed to retrieve data" >&2
fi
```
This script simplifies repeated data transfers and ensures data consistency.