scripts/shell/.local/bin/tmux-management

#!/usr/bin/env bash
# Open a tiled tmux window with one pane per host each in its own tmux session
# The local host is always the last (active) pane.
# Copyright 2021-2025 Bryan C. Roessler
# Licensed under the Apache License, Version 2.0

set -euo pipefail

# Configuration (override with env vars if desired)
HOSTS=(workstation laptop) # hosts in pane order
REMOTE_SESSION=${REMOTE_SESSION:-main} # tmux session on remotes
SYNCHRONIZE=${SYNCHRONIZE:-1} # 1 = broadcast keystrokes
INCLUDE_LOCAL=${INCLUDE_LOCAL:-1} # 0 = skip local host
LOCAL_SHELL_ONLY=${LOCAL_SHELL_ONLY:-0} # 1 = plain shell locally
DEBUG=${DEBUG:-0}

debug() { if (( DEBUG )); then echo "Debug: $*"; fi; }

# Returns 0 if $2 is found in nameref array $1
array_contains() {
  local -n arr=$1
  local needle=$2
  for element in "${arr[@]}"; do
    [[ "$element" == "$needle" ]] && return 0
  done
  return 1
}

LOCAL=$(hostname -s)

# Build TARGETS list so that LOCAL is always last
TARGETS=()
for h in "${HOSTS[@]}"; do
  [[ $h != "$LOCAL" ]] && TARGETS+=("$h")
done
if (( INCLUDE_LOCAL )); then
  TARGETS+=("$LOCAL")
fi

(( ${#TARGETS[@]} )) || { echo "No hosts to connect to."; exit 1; }

SESSION=$(IFS=-; echo "${TARGETS[*]}")
debug "Session : $SESSION"
debug "Targets : ${TARGETS[*]}"

# Re‑attach if session already exists
if tmux has-session -t "$SESSION" 2>/dev/null; then
  exec tmux attach -t "$SESSION"
fi

# Builds the command that will run inside a pane
open_cmd() {
  local tgt=$1
  if [[ $tgt == "$LOCAL" ]]; then
    if (( LOCAL_SHELL_ONLY )); then
      printf '%q -l' "${SHELL:-bash}"
    else
      printf 'tmux -L %q new -A -s %q' "${SESSION}_local" "$REMOTE_SESSION"
    fi
  else
    printf 'ssh -t %q tmux new -A -s %q' "$tgt" "$REMOTE_SESSION"
  fi
}

# Create the first pane
tmux new-session -d -s "$SESSION" -n "$SESSION" "$(open_cmd "${TARGETS[0]}")"

# Create remaining panes
for tgt in "${TARGETS[@]:1}"; do
  tmux split-window -t "$SESSION:0" -h "$(open_cmd "$tgt")"
done

tmux select-layout -t "$SESSION:0" tiled
((SYNCHRONIZE)) && tmux setw -t "$SESSION:0" synchronize-panes on

# Activate the last pane (local host)
local_index=$(( ${#TARGETS[@]} - 1 ))
tmux select-pane -t "$SESSION:0.$local_index"

exec tmux attach -t "$SESSION"