Overview

Tmux changed the bind syntax starting in version 2.4. The syntax changes are simple enough to make, however, some linux distros haven’t upgraded to a newer version of tmux. For example, RHEL 7.4 still has tmux 1.8 in its repositories by default while FreeBSD 11.1 has tmux 2.6. To ensure maximium backward compatibility with tmux viersions <2.4 the .tmux.conf should check the system’s version of tmux and act accordingly.

Config

First in the .tmux.conf lets have tmux set its version in an environment variable that will be referenced later:

run-shell "tmux setenv -g TMUX_VERSION $(tmux -V | cut -d' ' -f2)"

To set version specific bind options for vi mode append the following to .tmux.conf. The conditional will use bind-key -T copy-mode-vi for tmux versions >=2.4 and bind -t vi-copy for versions <2.4:

# vi Mode
set -g mode-keys vi

# Add some vi comfort
unbind p
bind p paste-buffer

# Check version due to bind changes in 2.4. bc return true as 1
if-shell '[ $(echo "$TMUX_VERSION >= 2.4" | bc -l) == 1 ]' \
"\
        bind-key -T copy-mode-vi v send -X begin-selection; \
        bind-key -T copy-mode-vi y send -X copy-selection; \
        bind-key -T copy-mode-vi V send -X rectangle-toggle; \
" "\
        bind -t vi-copy v begin-selection; \
        bind -t vi-copy y copy-selection; \
        bind -t vi-copy V rectangle-toggle; \
"

Save .tmux.conf after making the above modifications and relaunch tmux.

To validate these changes on tmux >=2.4 run the following from the tmux command prompt(.i.e "command seq + :" inside tmux):

list-keys -T copy-mode-vi

To validate in <2.4:

list-keys -t vi-copy

The bindings should be set in the list-keys output along with other default options.

That’s all there is to conditional config loading in tmux! Checkout my full .tmux.conf on my github repo for specifics.