In WSL (Windows Subsystem for Linux) you get access to a Linux terminal right inside of Windows 10. For the most part, it works great. However, when it comes to copying and pasting the contents of files from Linux into Windows, the option is obscured.
You can right-click the toolbar on the WSL terminal window, go to properties and enable the copy and paste features if you’re on one of the latest versions of it.
This will enable copy and paste from files. However, as you might also learn, this doesn’t appear to always work.. I wanted to copy the contents of a public key to a website to use SSH authentication. Which is where the next solution definitely works.
Piping to the clipboard
You can also use a lesser-known trick of piping the contents of a file using
clip.exe which will be the Windows clipboard. This always works for me, where enabling the above did not.
cat < ~/.ssh/id_rsa.pub | clip.exe