tmux_session_picker.sh

#!/bin/bash
# Tmux Session Picker — auto-creates and displays sessions on SSH login
# Source this file at the END of .bashrc or .zshrc (compatible with both)
#
# Setup:
#   1. Place at ~/.tmux_session_picker.sh
#   2. Add to .bashrc or .zshrc: [[ -f ~/.tmux_session_picker.sh ]] && source ~/.tmux_session_picker.sh
#
# Features:
#   - Auto-creates sessions for configured directory paths
#   - Displays a table with session name, window count, running processes, and last access
#   - Detects notable processes via pstree (customizable)
#   - Supports attach by number, by name, creating new sessions, or skipping tmux
#   - Re-displays after creating new sessions
#   - Only runs on interactive SSH login (not inside tmux, not with NOTMUX=1)
#
# Configuration:
#   Edit _TMUX_SESS_PAIRS below to customize pre-created sessions.
#   Format: "session_name=/path/to/directory"
#
# Display:
#   #    SESSION          WIN PROCESSES            LAST ACCESS
#   ---  ---------------- --- -------------------- -------------------
#   1)   dockergit *        1 claude               just now
#   2)   docs               1 vim                  5m ago
#   3)   home               1 -                    2h ago
#
#   [1-3] attach  [n] new  [s] skip
#   >

# === Configuration ===
# Pre-created sessions: "name=/path" pairs. Sessions created only if path exists.
_TMUX_SESS_PAIRS=(
  "project=/path/to/project"
  "config=/path/to/config"
  "home=$HOME"
)

# Notable processes to detect via pstree
_TMUX_NOTABLE_PROCS=(claude vim nvim docker node python pwsh htop)

# === Implementation ===
if command -v tmux >/dev/null 2>&1 &&
   [[ $- == *i* ]] && [[ -n "$SSH_TTY" ]] && [[ -z "$TMUX" ]] && [[ -z "$NOTMUX" ]]; then

    # Create sessions for valid paths
    for _pair in "${_TMUX_SESS_PAIRS[@]}"; do
        _sess_name="${_pair%%=*}"
        _sess_path="${_pair#*=}"
        if [[ -d "$_sess_path" ]] && ! tmux has-session -t "$_sess_name" 2>/dev/null; then
            tmux new-session -d -s "$_sess_name" -c "$_sess_path"
        fi
    done

    # Detect notable processes in a tmux session via pstree
    _tmux_procs() {
        local sid=$1
        local pids procs=""
        pids=$(tmux list-panes -t "$sid" -F '#{pane_pid}' 2>/dev/null)
        for _pid in $pids; do
            local tree
            tree=$(pstree -A "$_pid" 2>/dev/null) || continue
            for _proc in "${_TMUX_NOTABLE_PROCS[@]}"; do
                [[ "$tree" == *"$_proc"* ]] && procs="${procs:+$procs, }$_proc"
            done
        done
        printf '%s' "${procs:--}"
    }

    # Relative time since last activity in a session
    _tmux_age() {
        local sid=$1
        local now age_s
        now=$(date +%s)
        local last
        last=$(tmux display-message -t "$sid" -p '#{session_activity}' 2>/dev/null) || { printf '?'; return; }
        age_s=$(( now - last ))
        if (( age_s < 60 )); then printf 'just now'
        elif (( age_s < 3600 )); then printf '%dm ago' "$(( age_s / 60 ))"
        elif (( age_s < 86400 )); then printf '%dh ago' "$(( age_s / 3600 ))"
        else printf '%dd ago' "$(( age_s / 86400 ))"; fi
    }

    # Session picker with loop (re-displays after creating new sessions)
    while true; do
        _tmux_names=()
        _tmux_count=0

        printf '\n'
        printf '#    %-16s %s %-20s %s\n' 'SESSION' 'WIN' 'PROCESSES' 'LAST ACCESS'
        printf -- '---  %-16s %s %-20s %s\n' '----------------' '---' '--------------------' '-------------------'

        while IFS='|' read -r _sname _swins _satt; do
            (( _tmux_count++ ))
            _tmux_names[$_tmux_count]="$_sname"
            _label="${_sname}${_satt:+ *}"
            _procs=$(_tmux_procs "$_sname")
            _age=$(_tmux_age "$_sname")
            printf '%-4s %-16s %3s %-20s %s\n' "${_tmux_count})" "$_label" "$_swins" "$_procs" "$_age"
        done < <(tmux list-sessions -F '#{session_name}|#{session_windows}|#{?session_attached,*,}' 2>/dev/null)

        printf '\n[1-%d] attach  [n] new  [s] skip\n' "$_tmux_count"
        printf '> '
        read -r _choice

        case "$_choice" in
            s|skip)
                break
                ;;
            n|new)
                printf 'Session name: '
                read -r _new_name
                printf 'Start directory: '
                read -r _new_path
                _new_path="${_new_path:-$HOME}"
                if [[ -n "$_new_name" ]] && [[ -d "$_new_path" ]]; then
                    tmux new-session -d -s "$_new_name" -c "$_new_path"
                else
                    printf 'Invalid name or path.\n' >&2
                    continue
                fi
                ;;
            [0-9]*)
                if (( _choice >= 1 && _choice <= _tmux_count )); then
                    exec tmux attach -t "${_tmux_names[_choice]}"
                else
                    printf 'Invalid selection.\n' >&2
                fi
                ;;
            "")
                ;;
            *)
                # Try as session name directly
                if tmux has-session -t "$_choice" 2>/dev/null; then
                    exec tmux attach -t "$_choice"
                else
                    printf 'Unknown session: %s\n' "$_choice" >&2
                fi
                ;;
        esac
    done

    unset _pair _sess_name _sess_path _tmux_names _tmux_count _sname _swins _satt _choice _new_name _new_path _label _procs _age _pid _proc
fi