How to Download Files With cURL: The Ultimate Guide

The cURL command-line tool is a versatile workhorse for transferring data, and one of its most common and powerful uses is downloading files from the internet. Whether you are a developer pulling dependencies, a system administrator fetching updates, or a web scraper acquiring large datasets, mastering cURL for downloads is essential.

This guide will provide a comprehensive breakdown of the most important cURL flags for file downloading, including how to manage file names, handle interruptions, and, critically, how to use a proxy like Nstproxy to ensure your downloads are fast, reliable, and unrestricted.

1. The Basics: Saving the Downloaded File

By default, cURL prints the content of the file directly to your terminal's standard output. To save the content to a file, you need to use one of two main flags: -O or -o.

Option 1: Save with the Original File Name (-O)

The -O (uppercase O) flag instructs cURL to save the file using the remote file's name.

curl -O https://example.com/assets/large_report.pdf
# Result: Saves the file as 'large_report.pdf' in the current directory.

Option 2: Save with a Custom File Name (-o)

The -o (lowercase o) flag allows you to specify a custom name for the downloaded file.

curl -o my_custom_report.pdf https://example.com/assets/large_report.pdf
# Result: Saves the file as 'my_custom_report.pdf' in the current directory.

2. Essential Flags for Reliable Downloads

For real-world scenarios, especially when dealing with large files or unstable connections, these flags are indispensable.

Handling Redirects (-L)

Many download links use HTTP redirects (3xx status codes) to point to the final file location. Without the -L flag, cURL will download the redirect page content, not the file itself.

curl -L -O https://shorturl.com/file-link
# The -L flag tells cURL to follow any redirects until it reaches the final destination.

Resuming Interrupted Downloads (-C -)

If a large download is interrupted (e.g., due to a network error or power outage), you can resume it without starting over using the -C - flag. This tells cURL to automatically figure out where the previous download stopped and continue from that point.

curl -C - -O https://example.com/assets/massive_archive.zip
# cURL checks the size of the existing file and resumes the download.

Downloading Multiple Files

You can download multiple files in a single command by listing them after the -O flag.

curl -O https://example.com/file1.txt -O https://example.com/file2.txt
# Downloads both file1.txt and file2.txt, saving them with their original names.

Rate Limiting (--limit-rate)

To prevent your download from consuming all your bandwidth or to avoid triggering server-side rate limits, you can cap the transfer speed.

curl --limit-rate 500K -O https://example.com/big_data.zip
# Limits the download speed to 500 Kilobytes per second.

Silent Downloads (-s)

By default, cURL displays a progress meter. To suppress this output and run the download silently (useful for scripts), use the -s flag.

curl -s -O https://example.com/script.sh
# Downloads the file without showing the progress bar.

3. Downloading Files Through a Proxy (Nstproxy Integration)

When downloading files for web scraping or market research, you often need to use a proxy to bypass geo-restrictions or IP blocks. Nstproxy provides high-speed, reliable Residential and Datacenter Proxies perfect for this task.

To route your download through a proxy, you use the -x or --proxy flag, followed by the proxy details.

Using an Authenticated Nstproxy Residential Proxy

We will use a generic Nstproxy Residential Proxy endpoint for the example:

curl -x http://nstuser:[email protected]:12345 -O http://example.com/file.jpg

Handling Proxy Authentication Separately

If your proxy requires authentication, you can also use the -U or --proxy-user flag to pass the credentials, which can be cleaner for scripting:

curl -x http://gate.nstproxy.io:12345 -U nstuser:nstpwd -O http://example.com/file.jpg

4. cURL vs. Wget for Downloads

Both cURL and Wget are popular command-line tools for downloading files, but they have different strengths:

For single-file downloads, especially when integrating with proxies like Nstproxy for anonymity and speed, cURL is often the preferred tool due to its flexibility and extensive protocol support.

Conclusion

cURL is an incredibly powerful and flexible tool for file downloading. By mastering flags like -O for saving, -L for redirects, and -C - for resuming, you can ensure your downloads are efficient and reliable.

When your download tasks require bypassing restrictions or managing high volumes of requests, integrating a high-quality proxy is non-negotiable. Nstproxy is the best proxy provider for these tasks, offering the speed and anonymity needed to execute your cURL downloads successfully, every time.

Frequently Asked Questions (Q&A)

Q1: What is the difference between curl -O and curl -o?

A: curl -O (uppercase O) saves the downloaded file using the original file name from the remote server. curl -o (lowercase o) allows you to specify a custom name for the saved file.

Q2: How do I resume a download with cURL?

A: You can resume an interrupted download by using the -C - flag (note the hyphen). This tells cURL to continue the transfer from where it left off, based on the size of the partially downloaded file.

Q3: Can I use Nstproxy's SOCKS5 proxies for file downloads with cURL?

A: Yes. cURL fully supports SOCKS5 proxies. You would use the -x flag with the socks5:// protocol prefix, for example:
curl -x socks5://nstuser:[email protected]:12345 -O http://example.com/file.jpg

Q4: Why would I need a proxy to download a file?

A: You need a proxy to download a file if the file's source is geo-restricted (only available in certain countries), if the server has blocked your IP address due to previous activity, or if you are downloading many files in quick succession and need to distribute the requests across multiple IP addresses to avoid rate limits.

Q5: How do I download a file from an FTP server using cURL?

A: cURL supports FTP natively. You simply use the ftp:// protocol in the URL. If authentication is required, you can include it in the URL or use the -u flag:
curl -u "ftpuser:ftppwd" -O ftp://ftp.example.com/file.zip

References
[1] Nstproxy - Residential Proxies: https://www.nstproxy.com/products/residential
[2] Nstproxy - IPV6 Proxies: https://www.nstproxy.com/products/ipv6