Copy file contents to the clipboard in Linux terminal

You can do the following that will directly copy the content of id_rsa.pub to clipboard:

pbcopy < ~/.ssh/id_rsa.pub

xclip -sel c < input_file

will copy the contents of input_file to clipboard. xclip requires installation. To install

sudo apt install xclip

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-sel stands for -selection. c is for clipboard. Interchangeable.

Capable of much more, I advise reading its man page.

There is also xsel. This answer on Unix SE gives a very thorough answer to this exact question.

If you're copying from terminal (like if you use the cat command already posted), highlight the key details and use Ctrl + Shift + C. This should put it on your clipboard. You can also right click and select 'copy' from terminal.

xclip -selection clipboard -i < fileName

copies the content of file into clipboard