I always wanted to do this and found a nice and easy way of doing it. I wrote down the complete procedure just in case anyone else needs it.

First install a 16 kB program called xclip:

sudo apt-get install xclip

You can then pipe the output into xclip to be copied into the clipboard:

cat file | xclip

To paste the text you just copied, you shall use:

xclip -o

To simplify life, you can set up an alias in your .bashrc file as I did:

alias "c=xclip"alias "v=xclip -o"

To see how useful this is, imagine I want to open my current path in a new terminal window (there may be other ways of doing it like Ctrl+T on some systems, but this is just for illustration purposes):

Terminal 1:pwd | cTerminal 2:cd `v`

Notice the ` ` around v. This executes v as a command first and then substitutes it in-place for cd to use.

Only copy the content to the X clipboard

cat file | xclip

If you want to paste somewhere else other than a X application, try this one:

cat file | xclip -selection clipboard

On OS X, use pbcopy; pbpaste goes in the opposite direction.

pbcopy < .ssh/id_rsa.pub

I've created a tool for Linux/OSX/Cygwin that is similar to some of these others but slightly unique. I call it cb and it can be found in this github gist.

In that gist I demonstrate how to do copy and paste via commandline using Linux, macOS, and Cygwin.

Linux

_copy(){    cat | xclip -selection clipboard}_paste(){    xclip -selection clipboard -o}

macOS

_copy(){    cat | pbcopy}_paste(){    pbpaste}

Cygwin

_copy(){    cat > /dev/clipboard}_paste(){    cat /dev/clipboard}

Note: I originally just intended to mention this in my comment to Bob Enohp's answer. But then I realized that I should add a README to my gist. Since the gist editor doesn't offer a Markdown preview I used the answer box here and after copy/pasting it to my gist thought, "I might as well submit the answer."

cb

A leak-proof tee to the clipboard

This script is modeled after tee (see man tee).

It's like your normal copy and paste commands, but unified and able to sense when you want it to be chainable

Examples

Copy

$ date | cb# clipboard contains: Tue Jan 24 23:00:00 EST 2017

Paste

# clipboard retained from the previous block$ cbTue Jan 24 23:00:00 EST 2017$ cb | catTue Jan 24 23:00:00 EST 2017$ cb > foo$ cat fooTue Jan 24 23:00:00 EST 2017

Chaining

$ date | cb | tee updates.logTue Jan 24 23:11:11 EST 2017$ cat updates.logTue Jan 24 23:11:11 EST 2017# clipboard contains: Tue Jan 24 23:11:11 EST 2017

Copy via file redirect

(chronologically it made sense to demo this at the end)

# clipboard retained from the previous block$ cb < foo$ cbTue Jan 24 23:00:00 EST 2017# note the minutes and seconds changed from 11 back to 00