Bash wrapper to run only one command in a time

run_one.sh

#! /bin/bash

ENV_FILE=/etc/container_env

set -a
source "${ENV_FILE}"
set +a

function set_trap(){
  local function_name="${1}"
  local signal_name="${2}"

  local current_trap
  local current_code

  [[ -z "${function_name}" || -z "${signal_name}" ]] && return 1

  current_trap=$(trap -p "${signal_name}")
  if [[ -z "${current_trap}" ]];then
    eval "trap '${function_name}' ${signal_name}"
    return 0
  fi

  current_code=$(echo "${current_trap}" \
    |sed -E "s/trap -- (['\"]?)(.+)\1 ${signal_name}/\2/")
      eval "trap -- '${function_name};${current_code}' ${signal_name}"

  return 0
}

function file_lock(){
  local file_path="${1}"
  local lock_fd=200

  [[ -f "${file_path}" ]] || touch "${file_path}"

  eval "exec ${lock_fd}>${file_path}"
  flock -n "${lock_fd}" || return 1

  echo "${$}" > "${file_path}"
  return 0
}
export -f file_lock

function file_unlock(){
  local file_path="${1}"
  local lock_fd=200

  eval "exec ${lock_fd}>&-"
  return 0
}
export -f file_unlock


if [[ "${#}" -lt 1 ]];then
  echo "Usage: ${0} <command>"
  exit 1
fi

command=${*}
command_hash=$(echo "${command}"|md5sum|awk '{print $1}')
command_file="/tmp/run_one-${command_hash}.lock"

if ! file_lock "${command_file}";then
  echo "Command already running: ${command}"
  exit 0
fi

set_trap "rm -f ${command_file}" EXIT
set_trap "file_unlock ${command_file}" EXIT

${command}

# vi:syntax=sh