tmux scrollback

If you regularly use tmux then you might have a line like this in your config:

set -g terminal-overrides 'xterm*:smcup@:rmcup@'

The effect of this is that when the output of the inner terminal exceeds the terminal’s height it is allowed to spill over into the outer terminal’s scrollback history. So long as you don’t change windows within the tmux session you can use the scrollbar of your local terminal to review the history.

Under the covers this disables the inner terminal’s smcup and rmcup capabilities when ENV['TERM'] =~ /^xterm/. These capabilities are responsible for saving and restoring terminal history/state. By disabling them the output is allowed to spill over.


It seems all is well until it comes to using iTerm2 on OSX. Suddenly scrolling back in the outer terminal shows history from prior to the start of tmux. There are no end of suggestions about how to fix this, including “disable the status bar” and “it should just work”. Actually it’s fairly simple.

Enable the option under Preferences -> Profiles -> Terminal called:

Save lines to scrollback when an app status bar is present

To save doing this again in future you can copy and version control the config file at ~/Library/Preferences/com.googlecode.iterm2.plist