When it comes to downloading files from the internet, many professionals (myself included) turn to cURL. Over the years, I’ve experimented with numerous methods of transferring data, but based on our implemented research, cURL consistently stands out for its versatility and reliability. Whether you’re grabbing a single file or managing simultaneous downloads, cURL has you covered. In this guide, we’ll show you how to download files with cURL—both basic and advanced techniques—and also compare it with another popular tool, Wget.
Understanding cURL Command
cURL stands for “client URL,” and it’s a command-line tool used to transfer data to or from a server using protocols like HTTP, HTTPS, FTP, and more. One of cURL’s primary advantages is its simplicity. You can install it on most operating systems (Linux, macOS, Windows) and start downloading files almost immediately. It offers a wide array of options and flags, which means you can customize almost any aspect of the file transfer.
For more detailed information, you can consult the official cURL documentation or explore community-driven guides.
Basic File Download Processes with cURL
Downloading a file with cURL
To get started with cURL for file downloads, try a simple command:
This command fetches file.zip from the specified server and writes the response to your terminal (standard output). By default, cURL sends progress information to the standard error stream while displaying the file contents to standard output.
Understanding the output argument -o
Instead of printing the file contents to your terminal, you often want to save the file locally. You can do this by adding the -o (lowercase “o”) argument:
This saves the downloaded file as myFile.zip in your current directory. The -o option is key for most download scenarios, as it explicitly redirects the output from your terminal to a local file.
Basic cURL Command for Downloading Files
Although -o works well for specifying filenames, the -O (uppercase “O”) flag automatically uses the remote file’s name. For instance:
saves the file as archive.tar.gz, matching the original filename on the server.
Following redirects
Some downloads might involve URL redirections. By default, cURL will not follow them. To handle this automatically, append the -L flag:
According to the analysis aggregated by Ping Proxies, many failed downloads happen because users forget to follow redirects, so make sure to include -L if your URL points to a shortened or redirected link.
Output without -o
If you don’t use -o or -O, cURL writes the file’s contents directly to standard output. This can be useful when you want to chain commands together, for example:
In this scenario, you’re downloading a CSV file and immediately searching for lines that contain “keyword.”
Making cURL silent
Sometimes, you want to download files in the background without any output or progress bar. You can enable “silent” mode using:
The -s (or --silent) flag suppresses progress and error messages for a cleaner output.
Advanced File Download Techniques
Limiting download speed in cURL
If you’re on a limited bandwidth connection or want to throttle the download speed for testing, use the --limit-rate option:
This caps the download to 200 kilobytes per second. Our data suggests that limiting download speed is especially useful when you have multiple transfers running concurrently.
Secure file transfers in cURL
For secure transfers over HTTPS, cURL verifies the SSL certificate by default. To add more security, you can provide custom certificates or enforce stricter checks. Simply include appropriate options such as --cacert or --cert if you need advanced SSL/TLS configurations.
Downloading portions of a file with cURL --range
cURL supports partial downloads via the Range header, making it possible to fetch only a segment of the file:
This command retrieves just the first 1 MB of hugefile.bin. Depending on your needs, you can specify any byte ranges to resume or split large downloads.
Seeing download progress in cURL
By default, cURL provides a progress meter in the terminal. If you want a more detailed progress bar, you can use the -# option:
This displays a progress bar with percentage completion, making it easier to track download progress.
Following redirects in cURL
As mentioned earlier, -L ensures that cURL follows redirects to the final URL. This is commonly needed for file hosting services or link shorteners. If you notice that your file isn’t downloading properly, try adding -L to see if redirects might be the cause.
Options and Flags for cURL Downloads
Output Options
- -o <filename>: Save the file under a specified name.
- -O: Use the remote file’s name automatically.
- -: (dash) sends output to standard output, useful for piping data to other commands.
Using the -O Flag
The -O flag is straightforward:
It’s helpful for quick, one-off downloads when you trust the original naming conventions. If you’re downloading multiple files with different names, the -o option is more flexible because you can specify unique file names.
Limiting Download Rate
Throttling your download speed via --limit-rate is beneficial if you’re testing network conditions or ensuring you don’t overwhelm a server. According to the analysis aggregated by Ping Proxies, intentionally limiting download rates can also reduce the likelihood of triggering anti-scraping or rate-limiting measures on certain websites.
Following Redirects
As a reminder, use -L to follow HTTP 3xx redirects. This prevents errors when the file is hosted on a content delivery network (CDN) or behind a shortened URL.
Handling Various File Download Scenarios in cURL
Downloading multiple files
You can download multiple files by passing multiple URLs or using -O multiple times:
Alternatively, you can store a list of URLs in a file and use a loop in a shell script to download each one.
Resuming interrupted file downloads
If your download gets cut off, you can resume it (assuming the server supports resuming) with the -C - option:
This command continues the download from where it left off, preventing you from having to restart the entire file transfer.
Downloading files from authenticated URLs
When downloads require a username and password, include them in the command using the -u option:
Be sure to confirm that you’re using HTTPS or another secure protocol when transmitting sensitive credentials.
Customizing cURL Requests
Specifying a client in cURL
Sometimes, you may need to mimic a specific client or browser. You can set a custom user agent with the -A or --user-agent flag:
This can be helpful when certain servers only allow downloads from recognized user agents.
Using cURL with cookies
If you need to send or receive cookies (for example, to stay logged in), you can specify a cookie file:
Or save cookies with -c:
This approach is often required for downloads from sites that have login pages or session checks.
Comparing cURL with Wget
cURL vs. Wget
Both cURL and Wget are popular file transfer tools. However, they serve slightly different purposes:
- cURL: Excellent for flexible data transfers and scripting. It supports many protocols and can handle intricate authentication flows.
- Wget: Designed primarily for recursive website downloads, enabling you to mirror entire sites with a single command.
If you want a straightforward “spider” to crawl and retrieve full directories, Wget might be better. But if you’re looking for more control, advanced authentication, or partial downloads, cURL often takes the edge. Our data suggests that many professionals keep both tools in their toolkit, using cURL for one-off or API-oriented downloads and Wget for more extensive crawling.
Conclusion
cURL is a powerhouse for downloading files, offering both simplicity and versatility in a single command-line utility. Whether you’re transferring large files, automating repetitive tasks, or testing network constraints, cURL’s robust feature set makes it an essential tool in any developer or systems administrator’s arsenal.
The best way to master cURL is through hands-on experience. Experiment with different flags (-O, -L, --limit-rate, --range) and see how they influence your downloads. According to the analysis aggregated by Ping Proxies, a solid understanding of cURL helps not only with file management but also with diagnosing network issues and optimizing data transfer workflows.
Please note, our data suggests that building proficiency with cURL will significantly streamline your file download processes in both personal and professional settings.
