How to Use cURL to Download Files

In daily development and operations work, we often need to fetch files from remote servers. Whether it’s retrieving a text file, downloading a binary package, or pulling resources in bulk through automation scripts, cURL is a very practical tool. It not only supports multiple protocols (HTTP, HTTPS, FTP, etc.) but also provides a wide range of options to flexibly handle various download scenarios.

This article will guide you through how to use cURL to download files, along with detailed explanations of common issues.

Download Files

1. Fetch a Remote File

The simplest usage is to run the following in your terminal:

curl https://cliproxy.com/file.txt

This will print the content of the remote file directly to the terminal instead of saving it locally. If you just want to quickly check the file content, this is very convenient.

2. Save a Remote File

If you want to save the file locally, you can use the -O or -o options:

• -O: Save using the original filename from the remote server.
• -o: Save with a custom filename.

Example — Save with a specific filename:

curl -o do-bots.txt https://cliproxy.com/robots.txt

Even if the remote filename differs, you can name the file however you prefer.

Follow Redirects

Some download links involve redirects (e.g., short links redirecting to the actual file). By default, cURL does not follow redirects automatically, so you need to add the -L flag:

curl -L -O https://short.url/file

This ensures you get the final file correctly.

Download Files with Authentication

Some downloads require authentication, which usually falls into two categories: username/password and token-based.

Username/Password Authentication

curl -u username:password -O https://cliproxy.com/protected/file.zip

The -u option is used to pass the credentials.

Token-Based Authentication

In API scenarios, bearer tokens are commonly used:

curl -H "Authorization: Bearer <your_token>" -O https://cliproxy.com/api/download

This method is more secure and widely adopted.

Handle Timeouts, Retries, and Resume Downloads

Set a Timeout

To avoid being stuck too long:

curl --max-time 60 -O https://cliproxy.com/largefile.zip

Automatic Retries

When the network is unstable, you can add retries:

curl --retry 5 -O https://cliproxy.com/largefile.zip

Resume Interrupted Downloads

If the download is interrupted, you can resume with:

curl -C - -O https://cliproxy.com/largefile.zip

This avoids starting over from scratch.

Automate Downloads with Shell Scripts

If you need to download multiple files, write a simple script:

#!/bin/bash
urls=(
  "https://cliproxy.com/file1.zip"
  "https://cliproxy.com/file2.zip"
)
for url in "${urls[@]}"; do
  curl -O "$url"
done

Save as download.sh and run it.

Download Multiple Files at Once

You can also list multiple URLs directly in the command line:

curl -O https://cliproxy.com/file1.zip -O https://cliproxy.com/file2.zip

This downloads all files sequentially.

Handle SSL/TLS Certificate Issues

If the target site has certificate issues (e.g., self-signed), cURL may throw an error. You can temporarily bypass this with -k:

curl -k -O https://cliproxy.com/file.zip

⚠️ Note: Using -k reduces security, so use it only in test environments.

Troubleshooting Common Issues

1. Download failed → Check if the URL is correct and the server is accessible.
2. Empty file → Ensure you use -L if redirects are required.
3. Permission denied → Confirm if authentication or a token is needed.
4. Unstable network → Use --retry or -C - for resuming.

wget vs. cURL

• wget: Primarily focused on file downloading, especially suited for large files and recursive crawling. For example, to mirror an entire website:

wget -r -np -k https://example.com

This downloads the whole site and converts links for offline browsing.

• cURL: More versatile, supports multiple protocols (HTTP, HTTPS, FTP, SMTP, LDAP, etc.). It can also be used for API debugging. For example:

curl -X POST -H "Content-Type: application/json" \
-d '{"username":"test","password":"123456"}' \
https://api.example.com/login

This simulates an API login request — something wget cannot do.

FAQs

1. What’s the difference between -O and -o in cURL?

• -O: Save using the remote filename.
• -o: Save using a custom filename.

2. How do I resume an interrupted download with cURL?
Use the -C - option, for example:

curl -C - -O https://cliproxy.com/file.zip

3. Can cURL be used on Windows?
Yes. Windows users can install the official cURL package or use it via Git Bash / WSL.

Conclusion

This article introduced multiple methods for downloading files with cURL, including saving files, handling redirects, authentication, resuming downloads, batch downloads, and SSL issues. It also compared wget and cURL.

👉 If you’re mainly downloading files, wget may be better.
👉 But if you need API debugging or flexible download scenarios, cURL is the best choice.