While installing Heroku CLI there's a command I encountered. Here is the command:

curl -L https://cli-assets.heroku.com/apt/release.key | sudo apt-key add -

What does it mean and how does it work?


curl is a utility to download something from a link. By default, it writes to STDOUT (ie prints stuff from the link in the terminal)

The -L option to curl means:

-L, --location
         (HTTP/HTTPS)  If the server reports that the requested page has moved to a 
         different location (indicated with a Location: header and a 3XX response 
         code), this option will make curl redo the request on the new place...

The operator | is a pipe, which passes the output of the command before it as the STDIN of the command after it.

apt-key is a utility to add trusted keys to apt for repositories. You can see what add does with man apt-key:

add <filename>
         Add a new key to the list of trusted keys. The key is read from the 
         filename given with the parameter filename or if the filename is -
         from standard input.

As it mentions, - tells apt key add that the key file should be read from STDIN, which in this case is what was piped from the curl command, so, in sum:

Download whatever is at this link, even if it has moved, and add it as a trusted APT repository key.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.