TL;DR - Copying text from tmux is broken in OSX. A workaround is introduced along with a clean way of shimming it in to your setup. Here’s the obligatory “I don’t care how it works just give me something I can blindly run to fix it” snippet:

formula_url=https://raw.github.com/phinze/homebrew/tmux-macosx-pasteboard/Library/Formula/reattach-to-user-namespace.rb
brew install $formula_url --wrap-pbcopy-and-pbpaste

Doing software development on an OSX machine means living with a weird set of parents.

+ =

You’ve got your mother—Apple—all curves and style, and your father—UNIX—all sharp angles and beards. That penguin does look sort of uncomfortable all crammed in there, doesn’t he?

I hate it when mommy and daddy fight. It only hurts the children, who just want to be able to copy text from inside a tmux session.

What’s broken

If you’ve ever used tmux – the delightful little GNU screen replacement – on OSX, you may have run into an annoying little problem. The handy pbcopy and pbpaste commands that normally give access to the OSX clipboard mysteriously stop working from within tmux.

This leaves you CMD+option clicking to box select and copy in iTerm and then dealing with your paste including any trailing whitespace from the box you made. Annoying and inconvenient.

Why it’s broken

GitHub user ChrisJohnsen has done a great job of researching and explaining what’s happening here. I will defer to his awesome in-depth explanation of both the problem and his solution, which is at the core of our workaround.

Getting the fix in place

In order to make it easy to install, I’ve created a homebrew formula that will download and compile the reattach-to-user-namespace tool.

You can install it like so:

phinze:~$ brew install https://raw.github.com/phinze/homebrew/tmux-macosx-pasteboard/Library/Formula/reattach-to-user-namespace.rb

So ChrisJohnsen recommends setting the reattach-to-user-namespace command to wrap every shell session under tmux using it’s default-command option. This works perfectly fine, but I found that I didn’t like having a parent process execute every time I made a new tmux window or split. I really only want pbcopy and pbpaste to work again, so I’m content just wrapping those commands.

To make this simple, I’ve added a --wrap-pbcopy-and-pbpaste option to my formula which creates little shims in /usr/local/bin that look like this:

#!/bin/sh
cat - | reattach-to-user-namespace /usr/bin/pbcopy

#!/bin/sh
reattach-to-user-namespace /usr/bin/pbpaste

With these in place I’m perfectly content and back to my usual clipboard-piping ways.

What about other apps like vim?

The reattach-to-user-namespace utility can be wrapped around any binary that has become lost from the OSX clipboard for the same reasons. For example, wrapping this around vim will fix the + register to once again point to the system clipboard. Again, you could go so far as to use ChrisJohnsen’s recommendation of wrapping all your shell sessions with the command, but I’ve found it cleaner to just apply it judiciously to the affected area.

Inclusion in mxcl/homebrew

I’ve got myself a pull request submitted to the homebrew project proper, hopefully they’ll consider accepting it. That would make installing this as easy as brew install reattach-to-user-namespace. It’s not exactly a shoe-in for inclusion in the main homebrew repository, but I’ve included some justification on the description of the pull request.

https://github.com/mxcl/homebrew/pull/8016

If you think this would be useful to you, consider posting a “+1” comment to this thread.

However the pull request pans out, I’ll keep my branch up, since I’ll be using this workaround until a better solution turns up.