commit 498481c491a347d6b78a0231500578ef81f6d382
Author: Michael Krayer <michael.krayer@posteo.de>
Date:   Thu Mar 18 10:58:17 2021 +0100

    initial commit

diff --git a/session b/session
new file mode 100755
index 0000000..47eb76f
--- /dev/null
+++ b/session
@@ -0,0 +1,283 @@
+#!/bin/bash
+shopt -s nullglob
+
+## Setup configuration
+CONFIG_FILE="$HOME/.sessionrc"
+typeset -A config
+# Set defaults
+config=(
+    [socket_dir]="/tmp/"
+    [socket_base]="session-$UID"
+    [shell]="/bin/bash"
+    [redraw]="winch"
+)
+# Source from configuration file if available
+if [ -f "$CONFIG_FILE" ]; then
+  while read line
+  do
+    if echo $line | grep -F = &>/dev/null
+    then
+        varname=$(echo "$line" | cut -d '=' -f 1)
+        config[$varname]=$(echo "$line" | cut -d '=' -f 2- | envsubst)
+    fi
+  done < $CONFIG_FILE
+fi
+
+## Set some variables
+SOCKET_PREFIX="${config[socket_dir]}/${config[socket_base]}-"
+SOCKET_SUFFIX=".socket"
+
+# Exit codes
+EXIT_SUCCESS=0
+EXIT_INVALID_MODE=1
+EXIT_SESSION_EXISTS=2
+EXIT_SESSION_NOT_EXIST=3
+EXIT_ALREADY_IN_SESSION=4
+EXIT_INVALID_CONFIG=5
+EXIT_CONFIG_EXISTS=6
+EXIT_INVALID_CHOICE=7
+
+## Functions
+print_help() {
+  echo >&2 "Usage: $(basename $0) mode [args]"
+  echo >&2 "Manage detachable shell sessions using 'dtach'."
+  echo >&2 "Available modes: "
+  echo >&2 "  attach    | att  | a      attach to an existing session"
+  echo >&2 "  new       |      | n      create a new session"
+  echo >&2 "  terminate | term | t      terminate an existing session (SIGTERM)"
+  echo >&2 "  kill      |      | k      send SIGKILL to an existing session"
+  echo >&2 "  list      | ls   | l      list all available sessions"
+  echo >&2 "  info      |      | i      print information on a session"
+  echo >&2 "  help      |      | h      display this help message"
+  echo >&2 ""
+  echo >&2 "$(basename $0) attach [name]"
+  echo >&2 "  Attach to specified session. If no session name is provided, an interactive"
+  echo >&2 "  selection menu is provided. Use <Ctrl-\\> to detach."
+  echo >&2 ""
+  echo >&2 "$(basename $0) new [name]"
+  echo >&2 "  Create a new session. If no session name is provided, a generic name will"
+  echo >&2 "  be generated. Use <Ctrl-\\> to detach."
+  echo >&2 ""
+  echo >&2 "$(basename $0) terminate [name]"
+  echo >&2 "  Terminate a specified session. If no session name is provided, all sessions"
+  echo >&2 "  will be terminated upon confirmation."
+  echo >&2 ""
+  echo >&2 "$(basename $0) kill [name]"
+  echo >&2 "  Same as 'terminate' but SIGKILL is sent to the shell instead of SIGTERM."
+  echo >&2 ""
+  echo >&2 "$(basename $0) list"
+  echo >&2 "  List all available sessions."
+  echo >&2 ""
+  echo >&2 "$(basename $0) info [name]"
+  echo >&2 "  Print information on a specified session. If no session name is provided," 
+  echo >&2 "  information on all sessions will be printed. The output contains the session"
+  echo >&2 "  name, the timestamp of creation and the path of its socket."
+  echo >&2 ""
+  echo >&2 "$(basename $0) help"
+  echo >&2 "  Print this help message."
+  echo >&2 ""
+  echo >&2 "$(basename $0) is configured using the file '$CONFIG_FILE', which, if"
+  echo >&2 "non-existent, can be initialized with '$(basename $0) config generate'."
+}
+
+get_available_sessions() {
+  local socket_paths=(${SOCKET_PREFIX}*${SOCKET_SUFFIX})
+  local socket_names=()
+  for spath in ${socket_paths[@]}; do
+    sname=${spath##${SOCKET_PREFIX}}
+    sname=${sname%%${SOCKET_SUFFIX}}
+    socket_names+=("${sname}")
+  done
+  echo ${socket_names[@]}
+}
+
+get_session_path() {
+  echo "${SOCKET_PREFIX}${1}${SOCKET_SUFFIX}"
+}
+
+is_existing_session_path() {  
+  if [ -S $1 ]; then
+    true
+  else
+    false
+  fi
+}
+
+is_existing_session_name() {
+  is_existing_session_path $(get_session_path $1)
+}
+
+get_new_session_name() {
+  local ii=1
+  while is_existing_session_name $ii; do
+    ii=$((ii+1))
+  done
+  echo $ii
+}
+
+exit_if_in_session() {
+  if [ ! -z $DTACH_SOCKET_PATH ]; then
+    echo >&2 "Cannot attach to a session from within a session."
+    exit $EXIT_ALREADY_IN_SESSION
+  fi
+}
+
+exit_if_existing_session() {
+  if ! is_existing_session_name $session_name; then
+    echo >&2 "Session '$session_name' does not exist."
+    exit $EXIT_SESSION_NOT_EXIST
+  fi
+}
+
+exit_if_nonexisting_session() {
+  if ! is_existing_session_name $session_name; then
+    echo >&2 "Session '$session_name' does not exist."
+    exit $EXIT_SESSION_NOT_EXIST
+  fi
+}
+
+print_session_info() {
+  local session_name=$1
+  local session_path=$(get_session_path $session_name)
+  local session_time=$(date -r $session_path "+%Y-%m-%d %H:%M:%S")
+  printf "%-24s %-20s %s\n" "$session_name" "$session_time" "$session_path"
+}
+
+## Parse first argument (= mode argument)
+if [[ "$#" -lt 1 ]]; then
+  print_help
+  exit $EXIT_INVALID_MODE
+fi
+mode=$1
+shift
+
+## Now enter mode specific code
+case $mode in
+  "attach"|"att"|"a") 
+    exit_if_in_session
+    # If no session name specified: select interactively
+    if [ -z "$1" ]; then
+      sessions_avail=($(get_available_sessions))
+      if [ ${#sessions_avail[@]} -eq 0 ]; then
+        exit $EXIT_SUCCESS
+      fi
+      echo >&2 "Select a session (q to quit)"
+      select session_name in ${sessions_avail[@]}
+      do
+        if [ -z "$session_name" ]; then
+          exit $EXIT_SUCCESS
+        fi
+        exit_if_nonexisting_session $session_name
+        break
+      done
+    else
+      session_name=$1
+      exit_if_nonexisting_session $session_name
+    fi
+    session_path=$(get_session_path $session_name)
+    CMD="dtach -a $session_path -r ${config[redraw]}"
+    exec $CMD
+    ;;
+  "new"|"n")
+    exit_if_in_session
+    #PROMPT_COMMAND="echo -ne \"\033]0;$1 (on $HOSTNAME)\007\""
+    # PS1="\[\e]0;My Titlito\a\]>>"
+    # If no session name specified: generate a generic one
+    if [ -z "$1" ]; then
+      session_name=$(get_new_session_name)
+    else
+      session_name=$1
+      exit_if_existing_session $session_name
+    fi
+    session_path=$(get_session_path $session_name)
+    CMD="env DTACH_SOCKET_PATH=$session_path DTACH_SESSION_NAME=$session_name "
+    CMD+="dtach -c $session_path -r ${config[redraw]} ${config[shell]}"
+    echo $CMD
+    exec $CMD
+    ;;
+  "terminate"|"term"|"t"|"kill"|"k")
+    # Check if we are in terminate/kill mode
+    if [[ ${mode::1} == "k" ]]; then
+      SIGNAL="-9"  # SIGKILL
+      CLEANUP=1    # requires manual cleanup
+    else
+      SIGNAL="-15" # SIGTERM
+      CLEANUP=0
+    fi
+    # If no session name specified: terminate all sessions
+    if [ -z "$1" ]; then
+      read -p "Terminate all sessions? [y/N] " -n 1 -r
+      printf "\n"
+      case $REPLY in
+        "y"|"Y")
+          session_name=($(get_available_sessions))
+          ;;
+        *)
+          echo "no"
+          ;;
+      esac
+    else
+      session_name=$1 
+      exit_if_nonexisting_session $session_name
+    fi
+    for sname in ${session_name[@]}; do
+      spath=$(get_session_path $sname)
+      PID=$(fuser $spath 2> /dev/null)
+      CMD="kill $SIGNAL $PID"
+      exec $CMD
+      if [[ "$CLEANUP" -eq 1 ]]; then
+        CMD="rm $spath"
+        exec $CMD
+      fi
+    done
+    exit $EXIT_SUCCESS
+    ;;
+  "list"|"ls"|"l")
+    sessions_avail=($(get_available_sessions))
+    for sname in ${sessions_avail[@]}; do
+      printf "$sname"
+      if [[ "$sname" == "$DTACH_SESSION_NAME" ]]; then
+        printf "*"
+      fi
+      printf "\n"
+    done
+    exit $EXIT_SUCCESS
+    ;;
+  "info"|"i")
+    # If no session name specified: info for all sessions
+    if [ -z "$1" ]; then
+      session_name=($(get_available_sessions))
+    else
+      session_name=$1 
+      exit_if_nonexisting_session $session_name
+    fi
+    for sname in ${session_name[@]}; do
+      print_session_info $sname
+    done
+    exit $EXIT_SUCCESS
+    ;;
+  "help"|"h")
+    print_help
+    exit $EXIT_SUCCESS
+    ;;
+  "config")
+    if [[ "$1" != "generate" ]]; then
+      echo >&2 "Use '$(basename $0) config generate' to generate default configuration file."
+      exit $EXIT_INVALID_CONFIG 
+    fi
+    if [ -f "$CONFIG_FILE" ]; then
+      echo >&2 "Configuration file '$CONFIG_FILE' already exists. Please remove it first."
+      exit $EXIT_CONFIG_EXISTS
+    fi
+    printf "" > $CONFIG_FILE
+    for key in ${!config[@]}; do
+      echo "${key}=${config[$key]}" >> $CONFIG_FILE
+    done
+    exit $EXIT_SUCCESS
+    ;;
+  *)
+    echo >&2 "Invalid mode: ${mode}"
+    print_help
+    exit $EXIT_INVALID_MODE
+    ;;
+esac