tmux status: show VPN IP when tunnel is active

Add tmux-vpn-ip helper (parses ifconfig for utun* on macOS, falls back
to tun/wg/ppp on Linux) and a tmux-net wrapper that conditionally
emits "⌂ <local> / ⇡ <vpn>" when a VPN tunnel is up, or just "<local>"
when it's not. status-right now calls tmux-net.

.local/bin/tmux-net

@@ -0,0 +1,17 @@
+#!/bin/bash
+#
+# Emit the tmux status-bar network segment.
+#   No VPN:  "<local_ip>"
+#   VPN up:  "<local_ip> (local) / <vpn_ip> (vpn)"
+#
+
+set -u
+
+local_ip=$("$HOME/.local/bin/tmux-ip" 2>/dev/null || true)
+vpn_ip=$("$HOME/.local/bin/tmux-vpn-ip" 2>/dev/null || true)
+
+if [ -n "${vpn_ip:-}" ]; then
+  printf '\xe2\x8c\x82 %s / \xe2\x87\xa1 %s\n' "${local_ip:-}" "$vpn_ip"
+else
+  printf '%s\n' "${local_ip:-}"
+fi

.local/bin/tmux-vpn-ip

@@ -0,0 +1,24 @@
+#!/bin/bash
+#
+# Print the IPv4 of the first active VPN tunnel interface, if any.
+# Empty output when no VPN is up.
+#
+# macOS: utun*   Linux: tun*, wg*, ppp*
+
+set -u
+
+case "$(uname -s)" in
+  Darwin)
+    ifconfig 2>/dev/null | awk '
+      /^utun[0-9]+:/   { iface=$1; sub(":", "", iface); next }
+      /^[a-z]+[0-9]*:/ { iface="" }
+      iface != "" && $1 == "inet" { print $2; exit }
+    '
+    ;;
+  Linux)
+    if command -v ip >/dev/null 2>&1; then
+      ip -4 -o addr show 2>/dev/null \
+        | awk '$2 ~ /^(tun|wg|ppp)[0-9]+/ { sub("/.*","",$4); print $4; exit }'
+    fi
+    ;;
+esac

.tmux.conf

@@ -79,7 +79,7 @@ set -g pane-border-style fg=colour245
 set -g pane-active-border-style fg=colour39
 set -g message-style fg=colour16,bg=colour221,bold
 set -g status-left '#[fg=colour235,bg=colour252,bold] ❐ #S #[fg=colour252,bg=colour238,nobold]❯#[fg=colour245,bg=colour238,bold] #(whoami) '
-set -g status-right '#[bold][#[nobold,fg=colour229]#H#[fg=default] / #[fg=colour229]#(~/.local/bin/tmux-ip)#[fg=default,bold]]#[nobold,fg=colour255] %H:%M %d-%b-%Y '
+set -g status-right '#[bold][#[nobold,fg=colour229]#H#[fg=default] / #[fg=colour229]#(~/.local/bin/tmux-net)#[fg=default,bold]]#[nobold,fg=colour255] %H:%M %d-%b-%Y '
 set -g window-status-format '#[fg=colour235,bg=colour252,nobold] #(~/.local/bin/tmux-window-icon #{window_index}) #(pwd="#{pane_current_path}"; echo ${pwd####*/}) #W '
 set -g window-status-current-format '#[fg=colour234,bg=colour39,bold] [#[fg=colour232,bold]#{?window_zoomed_flag,#[fg=colour228],} #(~/.local/bin/tmux-window-icon #{window_index}) #(pwd="#{pane_current_path}"; echo ${pwd####*/}) #W #[fg=colour234,bold]] '
 set-option -g status-interval 60