Copy text from remote tmux to local x clipboard

Question

I ssh into my VPS and run tmux. I can copy/paste from the remote to local, and local to remote - using the mouse and shift.

But I don't know how to copy large quantities of text.

If I were working locally, I could do this: cat somefile.txt | xsel -b or cat somefile | xclip -selection clipboard to copy into the clipboard. (I can't do that of course as the remote server doesn't run x, and even so the clipboard would not match the one used in tmux.)

So, how do I copy text in the tmux session, and for it to be duplicated over the wire to my local system's clipboard?

UPDATE:
Actually, this is applicable even without tmux - how to copy-paste large buffers between a remote and local shell.

Answer 1

To have bidirectional clipboard (more here):

1. Run ssh with -X to enable X11 forwarding.

2. Install xsel (manipulate the X selection).

   sudo apt instal xsel
   

That's it. Now, to test remote → local run on the remote host:

time date +%Y-%m-%d_%T | xsel -b  # Or tee >(xsel -b) to get the output also on stdout

On local host:

echo "Time on server is $(xsel -b)"

time will show how long it took the command to copy the text to the clipboard.

Notes

• You can also use primary buffer instead:

  Selection options

  -p, --primary: operate on the PRIMARY selection (default).
  -b, --clipboard: operate on the CLIPBOARD selection.

• tmux buffer stack might be enough on some cases.

• -X Might need xauth on server.

• xsel depends on libx11-6 and libc6 (apt depends xsel).

• If you get xsel: Can't open display: (null) check this answer.

Answer 2

In addition to Pablo's excellent answer above, if you are doing esoteric DISPLAY stuff, e.g. X11 forwarding for clipboard but using local display for OpenGL / CUDA machine learning stuff, then you may want to redirect your displays.

If you siphon an X11-forwarded display off into a separate env var, then you can have the "best" of both worlds.

It can look something like this:

# Bash function.
personal-ssh-session() {  # Call manually
    if [[ ! -v _SSH_DISPLAY && -v DISPLAY ]]; then
        export _SSH_DISPLAY=${DISPLAY}
        echo "Using redirect _SSH_DISPLAY=${_SSH_DISPLAY}"
    fi
    export DISPLAY=:1
}


# Bash script, `tmux-copy.sh`
#!/bin/bash
set -e
if [[ -n "${_SSH_DISPLAY}" ]]; then
    export DISPLAY=${_SSH_DISPLAY}
fi
mkdir -p ~/tmp
tee ~/tmp/tmux-clipboard.txt | xclip -in -selection clipboard


# tmux bind command - be sure ${_DOTFILES} is set, or use something else
bind -T copy-mode-vi Enter send-keys -X copy-pipe \
    '${_DOTFILES}/tmux-copy.sh'

Example from https://github.com/eacousineau/dotfiles_template

• Run inside X11-forward SSH session: bash_aliases func
  • This will set DISPLAY to use local gfx card vs. X11 forwarding (most likely software rendering)
• Add script to handle redirect for clipboard; this also dumps current stuff in ~/tmp/tmux-clipboard.txt, just in case: bash script
• Tell tmux to use this script: tmux bind command