bash: sudo hack to work around the huge install script I use, where an installer does sudo -k halfway through :/

sudo-hack.sh

#!/usr/bin/env bash

# sudo enable-disable hack
#
# Copyright (c) 2013 "Cowboy" Ben Alman
# Licensed under the MIT license.
# http://benalman.com/about/license/

if [[ "$UID" == "0" ]]; then
  echo 'Error: Do not run this script as root or using sudo.'
  exit 1
fi

sudo_pipe=
sudo_rnd=$(python -c 'import os;print "-".join(str(ord(x)) for x in os.urandom(9))')
sudo_already=0; [[ ! "$(sudo -n test 2>&1)" ]] && sudo_already=1
function sudo() {
  if [[ ! "$sudo_pipe" ]]; then
    sudo_pipe=$(mktemp -d /tmp/sudo.XXXXXX)/pipe
    mkfifo $sudo_pipe
    local fns="$(declare -f sudo_enable sudo_disable sudo_quit sudo_daemon)"
    command sudo bash -c "$fns; sudo_daemon $$ $sudo_rnd $sudo_pipe $sudo_already $USER $(tty)"
  fi
  sudo_enable
  command sudo "$*"
  sudo_disable
}

function sudo_enable()  { echo "$sudo_rnd-enable"  > $sudo_pipe; }
function sudo_disable() { echo "$sudo_rnd-disable" > $sudo_pipe; }
function sudo_quit()    { echo "$sudo_rnd-quit"    > $sudo_pipe; }

function sudo_daemon() {
  [[ ! "$5" ]] && echo 'Error: no $USER environment variable?' && exit 1
  local parent_pid=$1
  local sudo_rnd="$2"
  local sudo_pipe=$3
  local sudo_already=$4
  local sudo_file sudo_dir d tty
  # Yes, I looked at the sudo source code.
  for d in /var/db /var/lib /var/adm /usr/adm; do
    [[ -d "$d" ]] && sudo_dir="$d/sudo/$5" && break
  done
  [[ ! "$sudo_dir" ]] && echo 'Error: sudo timestamp directory not found.' && exit 1
  sudo_file="$sudo_dir"
  # This might only apply to Ubuntu 12.04, dunno about other OSes.
  tty="${6##/dev/pts/}"; [[ -e "$sudo_dir/$tty" ]] && sudo_file="$sudo_dir/$tty"
  # Read commands from the pipe.
  while read cmd; do
    echo "??? $cmd"
    # Refresh sudo timestamp.
    if [[ "$cmd" == "$sudo_rnd-enable" ]]; then
      [[ ! -d "$sudo_dir" ]] && mkdir "$sudo_dir"
      touch "$sudo_file"
    # Remove sudo timestamp.
    elif [[ "$cmd" == "$sudo_rnd-disable" ]]; then
      touch -t 196912310000 "$sudo_file"
    # Quit.
    elif [[ "$cmd" == "$sudo_rnd-quit" ]]; then
      [[ $sudo_already == 1 ]] && touch "$sudo_file"
      break
    fi
  done <>$sudo_pipe >/dev/null 2>&1 &
  # Kill daemon when parent script exits, otherwise refresh sudo timestamp.
  while true; do
    sleep 1
    if kill -0 "$parent_pid"; then sudo_enable; else sudo_quit; break; fi
  done >/dev/null 2>&1 &
}

echo -e '>>> Running "sudo date" (should prompt ONLY if sudo timestamp was not already set)'
sudo date

echo -e '\n>>> Running command that does sudo -k for safety'
# brew install cowsay
sudo -k

echo -e '\n>>> Running "sudo date" (should not prompt)'
sudo date

echo -e '\n>>> Running command that uses sudo internally (should prompt)'
./sudo-test-internal-sudo.sh

echo -e '\n>>> Running "sudo date" (should NOT prompt)'
sudo date

echo -e '\n>>> Running command that uses sudo internally (should NOT prompt)'
sudo_enable
./sudo-test-internal-sudo.sh
sudo_disable

echo -e '\n>>> Running command that uses sudo internally (should prompt)'
./sudo-test-internal-sudo.sh

echo -e '\n>>> Running "sudo date" (should NOT prompt)'
sudo date

echo -e '\n>>> Any sudo timestamp from before running this script should be restored'

sudo-test-internal-sudo.sh

#!/usr/bin/env bash

echo ">>> >>> starting $0"
sudo bash -c "echo '>>> >>>' this command is run via sudo"
echo ">>> >>> ending $0"

usage.txt

$ sudo -k

$ ./sudo-hack.sh
>>> Running "sudo date" (should prompt ONLY if sudo timestamp was not already set)
Password:
Fri Sep 27 14:41:53 EDT 2013

>>> Running command that does sudo -k for safety

>>> Running "sudo date" (should not prompt)
Fri Sep 27 14:41:54 EDT 2013

>>> Running command that uses sudo internally (should prompt)
>>> >>> starting ./sudo-test-internal-sudo.sh
Password:
>>> >>> this command is run via sudo
>>> >>> ending ./sudo-test-internal-sudo.sh

>>> Running "sudo date" (should NOT prompt)
Fri Sep 27 14:41:59 EDT 2013

>>> Running command that uses sudo internally (should NOT prompt)
>>> >>> starting ./sudo-test-internal-sudo.sh
>>> >>> this command is run via sudo
>>> >>> ending ./sudo-test-internal-sudo.sh

>>> Running command that uses sudo internally (should prompt)
>>> >>> starting ./sudo-test-internal-sudo.sh
Password:
>>> >>> this command is run via sudo
>>> >>> ending ./sudo-test-internal-sudo.sh

>>> Running "sudo date" (should NOT prompt)
Fri Sep 27 14:42:03 EDT 2013

>>> Note: sudo timestamp from before running this script should be restored

$ sudo date
Password:

Tweaked and added to my dotfiles here https://github.com/cowboy/dotfiles/blob/a8825a248bf51492cbd0ca0ea69fa2fd0ba5c51e/bin/dotfiles#L18-L74