Guru Das Srinagesh

TIL: How to unify all three of Ubuntu's clipboards

02 Mar 2024

Yes, you read that right - Ubuntu (which uses the X server) has a grand total of three clipboards: As the Inter-Client Communication Conventions Manual (ICCCM) explains:

Selection Atoms

There can be an arbitrary number of selections, each named by an atom. To conform with the inter-client conventions, however, clients need deal with only these three selections:


Of these, only PRIMARY and CLIPBOARD are commonly used by applications. As explains:

There are two historical interpretations of the ICCCM:

a) use PRIMARY for mouse selection, middle mouse button paste, and explicit cut/copy/paste menu items (Qt 2, GNU Emacs 20)

b) use CLIPBOARD for the Windows-style cut/copy/paste menu items; use PRIMARY for the currently-selected text, even if it isn't explicitly copied, and for middle-mouse-click (Netscape, Mozilla, XEmacs, some GTK+ apps)

No one ever does anything interesting with SECONDARY as far as I can tell.

What led me to this discovery?

There are two main ways to copy and paste stuff from one application to another on Ubuntu:

  1. Select text using mouse, Ctrl-C, Ctrl-V
  2. Select text using mouse, paste using middle click of mouse.

It was when I found myself naturally mixing up these two methods and expecting this unsupported hybrid scheme to work that I grew frustrated and decided to investigate why the scheme that occurred to me naturally did not, in fact, work. Allow me to explain using a couple of scenarios.

Terminal → Terminal

As a heavy terminal and tmux user, my workflow involves frequently copying stuff I use tmux, so I need to copy stuff from one tmux pane to another. To achieve this, I use the second method above.

This is intuitive to me because the two operations occur in the same application and what the mouse selects, it copies, too. The first method also works, albeit with a twist: need to use Ctrl-Shift-C and Ctrl-Shift-V. So this is technically a third way of copying and pasting on Ubuntu.

Non-terminal application → non-terminal application

Example: copying from one Google Chrome tab to another.

Here, the first method is intuitive to me because it is what has been ingrained in me from a young age thanks to Windows.

Non-terminal application → Terminal

Example: copying from Google Chrome to the terminal.

Here, too, the first method is intuitive to me, albeit with a twist. The twist is that you need to paste using Ctrl-Shift-V in the terminal. So this is technically a fourth way of copying and pasting on Ubuntu.

Terminal → non-terminal application

Example: copying from the terminal to Google Chrome.

Here is where my brain crosses out disruptively. What is intuitive to me is copying by selecting the text using the mouse, and pasting using Ctrl-V. This does not work. This is what is intuitive to me because I used PuTTy on Windows for a long time for work and this is how it works there.

Really, this was the main use case that frustrated me because I frequently have to look up a compilation error message, or copy some logs to a chat client. I would select to copy using the mouse, paste using Ctrl-V, fail, then middle-click. I did this so many times that I found it disruptive to my workflow and had to fix this.

The fix: unify both clipboards

Install autocutsel and add this to your .bashrc:

autocutsel -s CLIPBOARD &
autocutsel -s PRIMARY   &

Now, Ubuntu behaves as though there is only a single, common clipboard for all applications - terminal or otherwise. To add to the above list, you now can:

  1. Select text using mouse, Ctrl-C, paste using middle click of mouse.
  2. Select text using mouse, paste using Ctrl-V

You can also go one step further and unify the third clipboard too, but I have not tried this out personally.

autocutsel -s SECONDARY &

StackOverflow helped me a lot 1 2 while researching this fix and learning more about the underlying architecture.

  1. Merge primary and clipboard X selections
  2. How can I merge the gnome clipboard and the X selection?