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Mastering the curl Command for Data Transfer

The curl command is a powerful tool for transferring data over the internet. In this blog post, we’ll explore some of the many ways that you can use curl in your Bash scripts and command-line workflows.

Downloading Files

One of the most common uses for curl is to download files from the internet. To download a file, simply pass the URL of the file to curl. For example, to download the latest version of the Ubuntu ISO file, you can use the following command:

curl -O <http://releases.ubuntu.com/20.04/ubuntu-20.04-desktop-amd64.iso>

The -O flag tells curl to save the file with the same name as it has on the server.

You can also specify a different name for the downloaded file by including the desired filename as the last argument.

curl -o new_name.txt <https://www.example.com/example.txt>

Uploading Files

curl can also be used to upload files to a server. To do this, use the -F flag followed by the name of the file to upload. For example:

curl -F "file=@/path/to/local_file.txt" <https://www.example.com/upload>

You can also use curl to upload multiple files at once.

curl -F "file1=@/path/to/local_file1.txt" -F "file2=@/path/to/local_file2.txt" <https://www.example.com/upload>

HTTP Requests

curl can also be used to make HTTP requests, including GET, POST, PUT, and DELETE requests.

For example, to send a GET request to a website:

curl <https://www.example.com>

To send a POST request with data:

curl -X POST -d "name=value" <https://www.example.com/form>

or you can use JSON

curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' <https://www.example.com/data>

You can also use curl to make authenticated requests. For example, to make a request with a basic authentication:

curl --user username:password <https://www.example.com>

Other features

curl also has a variety of other features that can be useful in certain situations.

For example, you can use the -L flag to follow redirects, and the -v flag to print verbose output, including the headers sent and received.

Additionally, curl supports the use of various protocols such as FTP, SFTP, HTTP, HTTPS, SCP, and many more.

curl <ftp://ftp.example.com>
curl sftp://user:password@example.com

Piping Curl With Other Commands

It’s also worth noting that curl can be used in conjunction with other command-line tools, such as awk, grep, and sed, to further manipulate and process the data returned by curl.

For example, you can use awk to extract specific data from the response, grep to search for specific patterns, or sed to replace text in the response.

curl <https://www.example.com> | awk '{print $2}'
curl <https://www.example.com> | grep "example"
curl <https://www.example.com> | sed "s/example/new_example/g"

In summary, curl is an essential command-line tool for any power user or advanced user working with data on the internet. With its simple syntax and powerful features, curl can help you automate your workflows, streamline your process, and extract valuable insights from data on the internet.

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