Fix Vim + Tmux yank/paste on unnamed register

Question

While using vim inside a tmux session I cannot yank or paste to the unnamed register. Going to a named register works fine, but unnamed never works.

Error is:

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Answer 1

To add a couple notes from my experience on OSX to the accepted answer:

• Make sure you do set clipboard=unnamed and not set clipboard=unnamedplus
• I had to kill my tmux server ($ killall tmux or $ tmux kill-session -a). Reloading the tmux configuration files showed that default-command was set but did not give vim access to the system clipboard.