using trap for SIGHUP (when user closes terminal window)

quicklock.sh

#!/usr/bin/env bash

export ql_quicklock_version="0.0.104"
export ql_source_file="$HOME/.quicklock/ql.sh";

export ql_gray='\033[1;30m'
export ql_magenta='\033[1;35m'
export ql_cyan='\033[1;36m'
export ql_orange='\033[1;33m'
export ql_green='\033[1;32m'
export ql_no_color='\033[0m'


on_ql_trap (){
   # echo something here
   ql_release_lock
}

ql_unlock_process(){
  kill -SIGUSR1 "$1"  #  kill <pid> given by $1, with SIGUSR1 signal...
}

 on_ql_conditional_exit (){

   if [[ $- == *i* ]]; then
       # if we are in a terminal just return, do not exit.
       # debugging: echo -e "${ql_orange}quicklock: since we are in a terminal, not exiting.${ql_no_color}";
      return 1;
   fi

    # debugging:  echo -e "${ql_orange}quicklock: since we are not in a terminal, we are exiting...${ql_no_color}";

    if [[ "$ql_prevent_exit" == "yes" || "$ql_prevent_exit" == "yes" ]]; then
       return 1;
    fi

    exit 1;

}

ql_noop(){
    echo "";
}


ql_remove_all_locks (){
   rm -rf "$HOME/.quicklock/locks/"*
}


ql_acquire_lock () {

  local name="${1}"  # the lock name is the first argument, if that is empty, then set the lockname to $PWD

  if [[ -z "$name" ]]; then
     echo -e "${ql_orange}quicklock: warning - no quicklock_name available so defaulted to \$PWD.${ql_no_color}"
     name="$PWD";
  fi

  mkdir -p "$HOME/.quicklock/locks"
  fle=$(echo "${name}" | tr "/" _)

  local qln="$HOME/.quicklock/locks/${fle}.lock"

  mkdir "${qln}" &> /dev/null || {
    echo -e "${ql_magenta}quicklock: could not acquire lock with name '${qln}'${ql_no_color}";
    echo -e "${ql_magenta}quicklock: someone else is using that lockname.${ql_no_color}";
    on_ql_conditional_exit;
    return 1;
  }

  my_named_pipe="${qln}/$$"
  mkfifo "${my_named_pipe}" &> /dev/null;  # add the PID inside the lock dir

  export ql_current_lockname="${qln}";
  trap on_ql_trap EXIT;
  trap on_ql_trap 0;
  trap on_ql_trap SIGHUP;


  echo -e "${ql_gray}quicklock: process id requesting lock: $$, parent process id: $(ps -o ppid= -p $$)${ql_no_color}."
  echo -e "${ql_green}quicklock: acquired lock with name '${qln}'${ql_no_color}"

  if [[ "$ql_allow_ipc" == "yes" ]]; then

    echo -e "quicklock: process is reading from named pipe to listen for incoming messages regarding releasing lock.";
    while read line; do ql_on_named_pipe_msg "$line" "$$"; done < ${my_named_pipe} &

  fi

}


ql_release_lock () {

    local quicklock_name="$ql_current_lockname";
    local is_force="nope";

    local last="$(echo ${@: -1})"
    if [[ "${last}" == "--force" ]]; then
      echo -e "${ql_magenta}quicklock: warning using --force.${ql_no_color}";
      is_force="yes"
    fi

   if [[ ! -z "$1" && "$1" != "--force" ]]; then
        quicklock_name="${1}";

   elif [[ -z "${quicklock_name}" ]]; then
        echo -e "${ql_orange}quicklock: warning - no quicklock_name available so defaulted to \$PWD.${ql_no_color}";
        quicklock_name="$PWD";
   fi

   if [[ "$quicklock_name" != "$HOME/.quicklock/locks/"* ]]; then

       quicklock_name=$(echo "${quicklock_name}" | tr "/" _)

      if [[ "$quicklock_name" =~ [^a-zA-Z0-9\-\_] ]]; then
        echo -e "${ql_magenta}quicklock: lockname has invalid chars - must be alpha-numeric chars only.${ql_no_color}"
        echo -e "${ql_magenta}quicklock: could not release lock with desired name -> '$fle'.${ql_no_color}"
        on_ql_conditional_exit
        return 1;
      fi

       quicklock_name="$HOME/.quicklock/locks/${quicklock_name}.lock";
   fi

   if [[ -z "${quicklock_name}" ]]; then
     echo -e "${ql_orange}quicklock: no lockname was defined. (\$quicklock_name was not set).${ql_no_color}";
     ql_maybe_fail;
     return 1;
   fi

   if [[ "$HOME" == "${quicklock_name}" ]]; then
     echo -e "${ql_orange}quicklock: dangerous value set for \$quicklock_name variable..was equal to user home directory, not good.${ql_no_color}";
     ql_maybe_fail;
     return 1;
   fi

   local current_pid="$$"
   local pid_inside="$(ls "${quicklock_name}" 2> /dev/null)";


   rm -r "${quicklock_name}" &> /dev/null &&
   { echo -e "${ql_cyan}quicklock: lock with name '${quicklock_name}' was released.${ql_no_color}";  } ||
   { >&2 echo -e "${ql_magenta}quicklock: no lock existed for lockname '${quicklock_name}'.${ql_no_color}"; ql_maybe_fail; }

   trap - EXIT; # clear/unset trap
   trap ql_noop EXIT;

}



# export all of the functions
export -f ql_remove_all_locks
export -f ql_maybe_fail;
export -f on_ql_conditional_exit;
export -f on_ql_trap;
export -f ql_acquire_lock;
export -f ql_release_lock;
export -f ql_get_lockowner_pid;
export -f ql_ls;
export -f ql_print_version;
export -f ql_unlock_process;
export -f ql_on_named_pipe_msg;
export -f ql_echo_current_lockname;
export -f ql_get_lockname;
export -f ql_write_message;
export -f ql_noop;

# that's it lulz