A Weird Imagination

Detachable X sessions

X forwarding

Normally with X, it's easy to run an application on a remote computer just by using X forwarding:

local:~$ ssh -X host
host:~$ echo $DISPLAY
host:~$ xterm

The xterm will appear on your local computer.

But if you want to continue working with that application on a different remote computer (or once you are physically in front of the computer it is running on), then you're out of luck.

For an application running in the terminal, you can start it inside a GNU Screen (or tmux) session which you can detach and then attach to again on another ssh connection.

GNU Screen for X

xpra (X Persistent Remote Applications) lets you move graphical applications from one computer to another in addition to fixing other problems with X forwarding. If you instead use xpra for the forwarding, then you can detach and reattach to the session at will.

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The clipboard in the command-line

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X clipboard

The X Window System, the basis for the GUI on most desktop Linux systems, defines how the clipboard works for copying and pasting between applications in Linux. One notable quark of X clipboard is that there's actually two clipboards in common use: the one you expect explicitly accessed via Copy and Paste menu items or key shortcuts called the CLIPBOARD and another one where you copy by selecting text and paste by pressing the middle mouse button called the PRIMARY selection.

X clipboard utilities

Occasionally it is useful to be able to read or write the clipboard at the command-line. For most uses, your terminal emulator's copy and paste options are probably enough. The primary use case I have for using a command-line program to interact with the clipboard is when I am uploading a file as a Gist:

<file xclip

The xclip utility will copy the contents of the file onto the clipboard (PRIMARY, not CLIPBOARD, by default) and then I can paste it on the Gist website.

My system also has xsel which is very similar to xclip. Wikipedia actually lists several such programs, including the unfortunately named xcopy, not to be confused with XCOPY.

GNU Screen copy mode

GNU Screen provides its own clipboard for copying information between the different windows of a screen session. ctrl+a, [ enters copy mode. In copy mode you can move the cursor using the arrow keys and page up/page down keys. Screen keeps a history (of configurable size), so you can scroll back pretty far. In fact, I use Screen's copy mode far more often for viewing the history in a terminal than for actually copying anything. You can exit copy mode either by using esc to cancel or enter once to mark the start of the selection and again to mark the end of it. Once you have copied something, ctrl+a, ] pastes the contents of the clipboard.