Follow Redirects in cURL, Follow Redirects in cURL. By Scott Robinson. 1 Comment. The cURL utility is a command line program often bundled Because browsers do HTTP redirection for you automatically. Curl, by default, do not support redirection. But with an extra argument, you can instruct curl to follow redirects. There are two options for this.
Tutorial
- If there is a chain of redirects, the -L option will only follow the redirects up to 500 times. You can control the number of maximum redirects that it will follow with the -max-redirs flag. Curl-L -max-redirs 700 example.com. If you set this flag to -1, it will follow the redirects endlessly. Curl-L -max-redirs -1 example.com.
- Follow Redirects with cURL in the CommandLine If you navigate directly to google in the command-line using curl, you will be taken to a 301 redirect URL.
Client URL, or cURL, is a library and command-line utility for transferring data between systems. It supports many protocols and tends to be installed by default on many Unix-like operating systems. Because of its general availability, it is a great choice for when you need to download a file to your local system, especially in a server environment.
In this tutorial, you’ll use the curl command to download a text file from a web server. You’ll view its contents, save it locally, and tell curl to follow redirects if files have moved.
Downloading files off of the Internet can be dangerous, so be sure you are downloading from reputable sources. In this tutorial you’ll download files from DigitalOcean, and you won’t be executing any files you download.
Step 1 — Fetching remote files
Out of the box, without any command-line arguments, the curl command will fetch a file and display its contents to the standard output.
Let’s give it a try by downloading the robots.txt file from Digitalocean.com:
You’ll see the file’s contents displayed on the screen:
Give curl a URL and it will fetch the resource and display its contents.
Saving Remote Files
Fetching a file and display its contents is all well and good, but what if you want to actually save the file to your system?
To save the remote file to your local system, with the same filename as the server you’re downloading from, add the --remote-name argument, or use the -O option:
Your file will download:
Curl Follow Redirect
Instead of displaying the contents of the file, curl displays a text-based progress meter and saves the file to the same name as the remote file’s name. You can check on things with the cat command:
The file contains the same contents you saw previously:
Now let’s look at specifying a filename for the downloaded file.
Step 2 — Saving Remote Files with a Specific File Name
You may already have a local file with the same name as the file on the remote server.
To avoid overwriting your local file of the same name, use the -o or --output argument, followed by the name of the local file you’d like to save the contents to.
Execute the following command to download the remote robots.txt file to the locally named do-bots.txt file:
Once again you’ll see the progress bar:
Now use the cat command to display the contents of do-bots.txt to verify it’s the file you downloaded:
The contents are the same:
Curl Redirect Output
By default, curl doesn’t follow redirects, so when files move, you might not get what you expect. Let’s look at how to fix that.
Curl Follow Redirection
Step 3 — Following Redirects
Thus far all of the examples have included fully qualified URLs that include the https:// protocol. If you happened to try to fetch the robots.txt file and only specified www.digitalocean.com, you would not see any output, because DigitalOcean redirects requests from http:// to https://:
You can verify this by using the -I flag, which displays the request headers rather than the contents of the file:
The output shows that the URL was redirected. The first line of the output tells you that it was moved, and the Location line tells you where:
You could use curl to make another request manually, or you can use the --location or -L argument which tells curl to redo the request to the new location whenever it encounters a redirect. Give it a try:
This time you see the output, as curl followed the redirect:
You can combine the -L argument with some of the aforementioned arguments to download the file to your local system:
Warning: Many resources online will ask you to use curl to download scripts and execute them. Before you run any scripts you have downloaded, it’s good practice to check their contents before making them executable and running them. Use the less command to review the code to ensure it’s something you want to run.
Conclusion
curl lets you quickly download files from a remote system. curl supports many different protocols and can also make more complex web requests, including interacting with remote APIs to send and receive data.
You can learn more by viewing the manual page for curl by running man curl.