There's some lines of my tmux.conf which I'd like executed only if my OS is Mac. However, I'd like to use my tmux.conf on multiple different operating systems. How can I make a command conditional to the OS on which tmux is currently running?


2 Answers 2


Use the if-shell command:

if-shell "uname | grep -q Darwin" "tmux-cmd1; tmux-cmd2;" "tmux-cmd3; tmux-cmd4"

You may want to put OS-specific commands in separate files, and execute them via the "source-file" command.

if-shell "uname | grep -q Darwin" "source-file .tmux-macosx" "source-file .tmux-linux"
  • 8
    The if-shell and run-shell tmux commands are currently asynchronous (as of tmux 1.7); they effectively run their shell command in the background, and any tmux commands that they run will only be executed after any commands that come after the if-shell or run-shell command itself (tmux is single-threaded). Effectively, if you use if-shell or run-shell in ~/.tmux.conf, the initial session (and any sessions, windows, or panes created explicitly created through ~/tmux.conf) will lack any tmux configuration arranged through if-shell or run-shell commands. Jan 22, 2013 at 3:01
  • 1
    @ChrisJohnsen if-shell works as expected for me with tmux 1.8. I am using it to set set-titles-string only for SSH: github.com/blueyed/dotfiles/commit/…
    – blueyed
    Feb 19, 2014 at 13:59
  • 3
    This should be accepted; it's the proper way to do it.
    – Chev
    Nov 14, 2014 at 18:06

Jimeh https://github.com/jimeh/dotfiles/commit/3838db8 has the answer. Also Chris Johnsen deserves a lot of credit for helping people on the GitHub issue here: https://Github.com/ChrisJohnsen/tmux-MacOSX-pasteboard/issues/8#issuecomment-4134987

Basically, you set up a shell script called safe-reattach-to-user-namespace that checks for the existence of the real reattach... command.

#! /usr/bin/env bash

# If reattach-to-user-namespace is not available, just run the command.
if [ -n "$(command -v reattach-to-user-namespace)" ]; then
  reattach-to-user-namespace $@
  exec "$@"

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