How to Download Files via cURL?
In this guide, I’ll walk you through how to use cURL to download files. I’ll cover everything from simple downloads to more advanced options, so by the end, you’ll feel confident using cURL for any download task you need. Let’s get started!
What is cURL and Why Should You Use It?
Before discussing the practical aspects, let’s first understand cURL and why it’s widely adopted across many domains.
cURL is a command-line tool that enables data transfer using a variety of network protocols. It is popular because of its flexibility and support for many protocols, including HTTP, HTTPS, FTP, SFTP, and more. For developers, sysadmins, and data engineers, it becomes an essential utility for interacting with web servers, automating tasks, and manipulating data.
Key features of cURL include:
- Downloading and uploading files using different protocols
- Handling redirects, cookies, and headers
- Allowing automation via scripts
- Supporting authentication and proxy connections
- Limiting bandwidth for controlled downloads
This versatility makes cURL an indispensable tool, especially when working with large-scale data transfers, APIs, or automating recurring tasks.
Best Proxies for cURL
When you are using cURL to download lots of files, you might encounter rate limit related errors. To avoid that, consider using proxies. Here are my top recommended rotating proxies:
- Bright Data: High-performance proxies with advanced features, ideal for comprehensive solutions.
- Smartproxy: Affordable, reliable proxies with global reach, perfect for web scraping.
- Oxylabs: Exceptional performance and support, great for businesses needing top-quality proxies.
- IPRoyal: Flexible rotation and pricing, suitable for small projects or as a secondary provider.
- SOAX: Premium proxies with precise targeting and multiple rotation settings at competitive prices.
- NetNut: Extensive capabilities for large-scale scraping, but basic documentation and dashboard.
- Infatica: Affordable, ethically-sourced proxies with robust performance for businesses.
Please note, I am NOT affiliated with any of the providers mentioned here.
Basic cURL Commands for Downloading Files
Before we discuss the more advanced features, it’s crucial to understand how to use the most basic cURL commands to download files.
1. Simple File Download with cURL
Let’s start with the most basic operation — downloading a file using cURL. This can be done with a straightforward command:
curl -O https://example.com/file.zip
The -O flag tells cURL to download the file and save it with the same name as the one specified in the URL. For example, if you download a file named file.zip, it will be saved locally.
2. Specifying a Different Filename
You may want to rename the downloaded file to avoid overwriting existing files or simply to follow a specific naming convention. Use the -o option followed by the desired filename:
curl -o newfile.zip https://example.com/file.zip
This command will download the file but save it as newfile.zip instead of the default filename.
Advanced cURL Commands for Efficient File Transfers
Once you’re comfortable with the basic download commands, it’s time to explore more advanced options that give you greater control over your file downloads.
Handling Redirects
In many cases, URLs might redirect to another location. By default, cURL doesn’t follow redirects unless explicitly told to do so. To make sure cURL follows HTTP redirects, use the -L flag:
curl -L -O https://example.com/redirectedfile.jpg
This command ensures that if the URL redirects to another location, cURL will follow the redirect and download the file from the final destination.
Downloading Multiple Files Simultaneously
If you need to download several files at once, you don’t have to run multiple cURL commands. cURL supports downloading multiple files with a single command. You can list each file, separated by a space, or use curly braces for a common pattern.
Specific Files
curl -O https://example.com/file1.jpg -O https://example.com/file2.jpg
Pattern Matching
curl -O https://example.com/files/{file1.jpg,file2.jpg,file3.jpg}
Range of Files
curl -O https://example.com/files/file[1-3].jpg
These techniques make it easy to automate the download of multiple related files in a single command, saving you time and effort.
Controlling Download Speed
If you are working on a shared network or want to limit the bandwidth consumption for a specific download, cURL offers the — limit-rate option. This allows you to set a maximum download speed to prevent overwhelming your server or network:
curl — limit-rate 500k -O https://example.com/largefile.zip
In this example, the download speed is limited to 500 KB per second. You can adjust this value based on your network’s bandwidth.
Silent Mode for Background Operations
You may want to download files without seeing cURL’s progress meter or other verbose output when running scripts. The -s flag enables silent mode, making the operation less noisy:
curl -s -O https://example.com/file.jpg
This command downloads the file without displaying the usual progress information, making it ideal for background tasks or when you want to reduce the clutter in the terminal.
Resuming Interrupted Downloads
If your internet connection drops or the download is interrupted, cURL can resume the transfer from where it left off. Use the -C option followed by a dash (-) to instruct cURL to continue from the last byte:
curl -C - -O https://example.com/largefile.zip
This feature is handy when downloading large files from unstable networks or slow servers.
Handling Authentication and Proxies
Sometimes, you may need to authenticate or route your downloads through a proxy server. Here’s how you can handle these cases with cURL.
Authentication for HTTP/FTP Downloads
When downloading from a server that requires authentication, you can use the -u option followed by your username and password:
curl -u username:password -O https://example.com/protectedfile.zip
Be cautious using this method, as exposing your credentials directly in the command can be insecure. Consider storing the credentials in a .netrc file or using environment variables.
Downloading Through a Proxy Server
If you need to route your download through a proxy server, use the -x option followed by the proxy’s address:
curl -x http://proxyserver:port -O https://example.com/file.zip
For proxy authentication, append your credentials:
curl -x http://username:password@proxyserver:port -O https://example.com/file.zip
cURL supports HTTP, HTTPS, and SOCKS proxies, so you can choose the one that fits your use case.
Debugging and Logging cURL Operations
When working with cURL, sometimes you need to inspect the details of your request and response. This is where the verbose mode comes in handy. Use the -v flag to display detailed information about the request:
curl -v https://example.com/file.zip
This will output headers, cookies, and other useful information to help debug issues, especially when interacting with APIs or web servers.
If you only need the HTTP status code to determine the success of your request, you can use the following:
curl -w "%{http_code}" -O https://example.com/file.zip
This command will print the HTTP status code after the download, which can be useful for checking the file transfer status.
cURL Best Practices and Common Mistakes
To make the most of cURL, it’s important to be mindful of some best practices and avoid common mistakes.
Best Practices
Use Configuration Files: If you’re frequently running the same cURL commands, consider using a configuration file to store your options. This helps you avoid repetition and keeps your scripts clean.
curl -K ~/.curlrc -O https://example.com/file.zip
Check Exit Codes: After executing a cURL command, always check the exit code to ensure the download was successful. A non-zero exit code usually indicates an error.
if [ $? -eq 0 ]; then
echo "Download successful"
else
echo "Download failed"
fi
Secure Authentication: Avoid exposing sensitive credentials directly in your cURL commands. Instead, store your credentials safely in environment variables, .netrc files, or secure vaults.
Common Mistakes
- Ignoring SSL Verification: While it might be tempting to use the -k flag to bypass SSL/TLS verification, this opens you up to potential security risks, such as man-in-the-middle attacks. Always verify SSL certificates when dealing with sensitive data.
- Improper URL Encoding: If your URLs contain special characters (e.g., spaces, & symbols), URL-encode them properly to avoid errors.
- Misunderstanding HTTP Methods: When interacting with APIs, ensure you’re using the correct HTTP method (GET, POST, PUT, etc.). Using the wrong technique can lead to failed requests.
Conclusion
cURL is a versatile tool for downloading files, automating tasks, and interacting with web servers. By learning its different options and flags, you can make your file transfers smoother and faster. It handles large files, automates repetitive jobs, and saves time. Whether you’re a developer, a sysadmin, or just someone who wants to make downloading easier, cURL is a reliable solution.
