shell script skeleton that accepts key=value parameters and sets them as shell variables. function names that are passed in are executed in order

shell script skeleton v2

#!/bin/bash

set -o nounset
set -o errexit
set -o pipefail
set -o errtrace
set -o functrace

export _settings_names=()
export _settings_defaults=()

.main(){
  export _black="$(tput setaf 0)"
  export _red="$(tput setaf 1)"
  export _green="$(tput setaf 2)"
  export _yellow="$(tput setaf 3)"
  export _blue="$(tput setaf 4)"
  export _magenta="$(tput setaf 5)"
  export _cyan="$(tput setaf 6)"
  export _white="$(tput setaf 7)"
  export _reset="$(tput sgr0)"
  export _bold="$(tput bold)"
  export _blink="$(tput blink)"
  export _reverse="$(tput smso)"
  export _underline="$(tput smul)"
  export _scriptdir="$( dirname "$( readlink -f "${BASH_SOURCE[0]}" )")"
  export _runout=${TMP:-/tmp}/.$$.run
  export _rootdir=${_rootdir:-$(pwd)}
  export _scriptconf="$_scriptdir/.$(basename ${BASH_SOURCE[0]}).conf"
  
  trap .on.exit EXIT
  trap '.on.error ${LINENO} ${BASH_LINENO[@]}' ERR

  # settings defaults
  local _i
  for (( _i = 0 ; _i < ${#_settings_names[@]} ; _i++ )){
    export ${_settings_names[_i]}="${_settings_defaults[_i]}"
  }

  # override default settings with config file
  [[ -f $_scriptconf ]] && source $_scriptconf

  # override config file with command line params
  for param in $@ ; do
    if [[ $param =~ .*\=.* ]]; then
      local readonly _param_name="${param%%=*}"
      local readonly _param_val="${param#*=}"
      shopt -s nocasematch
      case $_param_val in
        yes|on|true) _param_val=1;;
        no|off|false) _param_val=0 ;;
      esac
      shopt -u nocasematch
      export ${_param_name}="${_param_val}"
    fi
  done

  local _do_default=1
  local readonly _script_functions=$(typeset -f | awk '/ \(\) $/ {print $1}' | { grep -ve '^\.' || true; } )
  for param in $@; do
    [[ $param =~ .*\=.* ]] && continue
    for fn in ${_script_functions[@]}; do
      if [[ $param == $fn ]]; then
        $fn
        continue 2
      fi
    done
    .error "Command not found: $param"
    return 1
  done

  return 0
}

.error(){
  echo -e "${_red}$*${_reset}" >&2
}

.warn(){
  echo -e "${_yellow}$*${_reset}" >&2
}

.info(){
  echo -e "${_green}$*${_reset}" >&2
}

.msg(){
  echo -e "${_reset}$*${_reset}" >&2
}

.write.settings(){
  local _i
  :>$_scriptconf
  for (( _i = 0 ; _i < ${#_settings_names[@]} ; _i++ )){
    local _var=${_settings_names[_i]}
    echo "${_var}=\"${!_var}\"" >> $_scriptconf
  }
}

.on.exit(){
  local _ret=$?
  rm -f $_runout
  .write.settings
  exit $_ret
}

.on.error(){
  local _ret=$?
  local _line=$1
  shift
  .error "Line $_line failed with $_ret"
  .msg "Call stack:"
  .error "  $_line: $(sed -n ${_line}p $0 | awk '{gsub(/^ +| +$/,"")} {print $0}')"
  for item in $@; do
    [[ $item > 0 ]] && .warn "  $item: $(sed -n ${item}p $0 | awk '{gsub(/^ +| +$/,"")} {print $0}')"
  done
  [[ -f $_runout ]] && cat $_runout
  exit $_ret
}

.run(){
  local _msg="$1"
  shift
  echo -e "$_red COMMAND FAILED $_reset" > $_runout
  echo -e "$_yellow $@ $_reset" >> $_runout
  echo "" >> $_runout
  ($@) >> $_runout 2>&1 &
  local _pid=$!
  local _spin='-\|/'
  local i=0
  while kill -0 $_pid 2>/dev/null; do
    i=$(( (i+1) %4 ))
    printf "\r$_yellow $_msg ${_spin:$i:1} $_reset"
    sleep .1
  done
  wait $_pid
  rm $_runout
}

--help(){
  cat <<EOF

Usage:$_green $0 ${_magenta}<parameter=value ...> ${_cyan}<command ...> ${_reset}

The ${_underline}${_magenta}parameter=value${_reset} list is optional and will override settings saved in the config file.
Multiple parameters and commands can be passed. Commands are executed in the order given.

$_cyan    settings $_reset -  Show or set script settings
$_cyan       debug $_reset -  Start debugging the next command

EOF
}
-help(){ --help; }
help(){ --help; }
--?(){ --help; }
-?(){ --help; }
?(){ --help; }

--settings(){
  .msg "The following settings are defined:"
  local _i
  for (( _i = 0 ; _i < ${#_settings_names[@]} ; _i++ )){
    local readonly _var=${_settings_names[_i]}
    printf "%25s:%s\n" "${_cyan} $_var ${_reset}" "${_magenta} ${!_var} ${_reset}"
  }
}
-settings(){ --settings; }
settings(){ --settings; }
--setting(){ --settings; }
-setting(){ --settings; }
setting(){ --settings; }

--debug(){ set -x; }
-debug(){ --debug; }
debug(){ --debug; }

.main $@
exit 0