My .tmux.conf ( usable across multi-platforms including OS X | Linux | Cygwin )

.tmux.conf

set-option -g default-terminal "xterm-256color"
set-window-option -g xterm-keys on

run-shell "tmux setenv -g TMUX_VERSION $(tmux -V | cut -c 6-)"

setw -g mode-keys vi

unbind C-b

# remap prefix to Control + Space
set -g prefix C-Space

# bind 'C-Space C-Space' to type 'C-Space'
bind C-Space send-prefix

# set small delay for each command
set -sg escape-time 1

set -g display-panes-time 4000

bind \ split-window -h -c '#{pane_current_path}'
bind - split-window -v -c '#{pane_current_path}'

bind h select-pane -L
bind j select-pane -D
bind k select-pane -U
bind l select-pane -R

bind -r H resize-pane -L 5 
bind -r J resize-pane -D 5 
bind -r K resize-pane -U 5 
bind -r L resize-pane -R 5 

bind @ respawn-pane -k

bind C-b copy-mode

bind -T copy-mode-vi v send-keys -X begin-selection

# To prevent some garbage characters from being printed to screen after copying or selecting something
# See https://www.reddit.com/r/tmux/comments/2xgrf8/garbage_characters_printed_to_screen_after_a/
set -g set-clipboard off
setw -g mouse on
#set -g mouse-select-pane on
#set -g mouse-resize-pane on
#set -g mouse-select-window on

# set color of active pane
if-shell -b '[ `echo "$(tmux -V | grep -o "[2-9]\.[0-9]\+") >= 2.8" | bc` -eq 1 ]' \
    'set -g pane-border-style bg=black,fg=white; set -g pane-active-border-style bg=black,fg=green' \
    'set -g pane-border-fg colour235; set -g pane-border-bg black; set -g pane-active-border-fg green; set -g pane-active-border-bg black'

# color status bar
#set -g status-bg colour235
#set -g status-fg white

# disable status bar
set -g status off

if-shell 'uname | grep -q Darwin' \
    'source-file ~/.tmux.conf.osx' \
    'if-shell "uname | grep -q CYGWIN" "source-file ~/.tmux.conf.cygwin" "source-file ~/.tmux.conf.linux"'

.tmux.conf.cygwin

# Copy the current buffer to system clipboard
bind C-c run "tmux save-buffer - | cat >/dev/clipboard" \

# Copy system clipboard to the current buffer and then paste the content
bind C-v run "cat /dev/clipboard | tmux load-buffer - && tmux paste-buffer" \

# Copy selection using a vi-like command; also copy it to system clipboard
if-shell -b '[ `echo "$(tmux -V | grep -o "[2-9]\.[0-9]\+") >= 2.4" | bc` -eq 1 ]' \
    'bind -T copy-mode-vi y send-keys -X copy-pipe "cat >/dev/clipboard"' \
    'bind -t vi-copy y copy-pipe "cat >/dev/clipboard"'
    

.tmux.conf.linux

# If you prefer xclip, use : 
# bind C-c run "tmux save-buffer - | xclip -i -sel clipboard"
# bind C-v run "tmux set-buffer \"$(xclip -o -sel clipboard)\"; tmux paste-buffer" 

# Copy the current buffer to system clipboard
bind C-c run "tmux save-buffer - | xsel --clipboard --input"

# Copy system clipboard to the current buffer and then paste the content
bind C-v run "xsel --clipboard --output | tmux load-buffer - && tmux paste-buffer"

# Copy selection using a vi-like command; also copy it to system clipboard
if-shell -b '[ `echo "$(tmux -V | grep -o "[2-9]\.[0-9]\+") >= 2.4" | bc` -eq 1 ]' \
    'bind -T copy-mode-vi y send-keys -X copy-pipe "cat | xsel --clipboard --input"' \
    'bind -t vi-copy y copy-pipe "cat | xsel --clipboard --input"'

.tmux.conf.osx

# Copy selection using a vi-like command; also copy it to system clipboard
bind -T copy-mode-vi y send-keys -X copy-pipe "pbcopy"

Thanks!

-if-shell -b '[ "$(echo "${TMUX_VERSION:0:3} >= 2.8" | bc)" = 1 ]' \
+if-shell -b '[ `echo "$(tmux -V | grep -o "[2-9]\.[0-9]\+") >= 2.8" | bc` -eq 1 ]' \

Shell syntax for if-shell should conform to POSIX on some system. (E.g., Ubuntu)