Ubuntu/Linux Mint Update Script

#!/bin/bash
## This script updates your system's packages, then reports
## whether or not a reboot is required.
##
## A "-y" parameter assumes "yes" and upgrades without
## prompting. (Useful when upgrading multiple systems.)
## 
## http://www.HaganFox.net/Main/UbuntuUpdateScript

##  SETTING
##
##  Prevents a sync if the local package index is up-to-date
##  The index is "up-to-date" for this many minutes (0 = always sync)
recent_sync=10

##  Get this script's basename
script_name=${0##*/}

##  Check for the "assume-yes" parameter
if [ "$1" = "-y" ]; then assumeyes="-y"; fi

##  Check for the prerequisite package
##  If it's not installed, offer to install it
prereq="update-notifier-common"
if [ $(dpkg-query -W -f='${Status}' $prereq 2>/dev/null \
 | grep -c "ok installed") -eq 0 ]
then
  echo
  echo "The \"$prereq\" package is not installed. It's"
  echo "required to determine whether a reboot will be required."
  echo
  read -p "Install $prereq now? [Y/n]? " choice
  case "$choice" in 
    y|Y|yes|''  ) sudo apt-get install $prereq;;
  esac
fi

##  Determine if the package database needs to be synchronized
sync_age=$(expr $(date -d now +%y%m%d%H%M)\
 - $(date -r /var/lib/apt/periodic/update-success-stamp +%y%m%d%H%M))
if [ $sync_age -lt $recent_sync ]; then
  sync_current="Package database was synchronized $sync_age minutes ago."
fi

##  Sync the local package database and upgrade
loglinesb4=$(wc -l </var/log/dpkg.log) # Count logs lines b4 upgrading
if command -v apt >/dev/null ; then # System has APT 1.0 or greater
  if [ "$sync_current" ]; then echo $sync_current
  else sudo apt update
  fi
  sudo apt-get $assumeyes --with-new-packages upgrade
  if [ $? -ne 0 ]; then 
    # --with-new-packages is not understood by apt-get
    echo "$script_name: Switching to \"apt upgrade\""
    sudo apt $assumeyes upgrade
  fi
  if [ $? -ne 0 ]; then
    # -y is not understood by apt
    aptget_fallback=1
    echo "$script_name: Switching to \"apt-get dist-upgrade\""
    sudo apt-get $assumeyes dist-upgrade
  fi
else # Ubuntu 12.04
  if [ "$sync_current" ]; then echo $sync_current
  else sudo apt-get update
  fi
  sudo apt-get $assumeyes dist-upgrade
fi

##  Report the packages that were installed
loglinesafter=$(wc -l </var/log/dpkg.log) # how many lines now?
newloglines=$((loglinesafter-loglinesb4)) # how many new lines?
if [ $newloglines -ne 0 ]; then
  echo
  echo "$script_name: Installed-packages list (from logfile):"
  tail -$newloglines /var/log/dpkg.log \
   | grep 'status installed' \
   | awk '{$1=$2=$3=""; print substr($0,4)}'
fi

##  If a -y parameter caused fallback to "apt-get dist-upgrade"
if [ "$aptget_fallback" ]; then
  echo
  echo "$script_name notice:" 
  echo "\"apt-get dist-upgrade\" was used because the -y parameter"
  echo "cannot be used together with \"apt upgrade\" on this system."
fi

##  Exit if the update-notifier-common package is missing
if [ $(dpkg-query -W -f='${Status}' $prereq 2>/dev/null \
 | grep -c "ok installed") -eq 0 ];
then
  echo 
  echo "$script_name: Unable to determine whether a reboot is required"
  echo "$script_name: because \"$prereq\" is not installed."
  echo
  exit
fi

##  Report the reboot-required status
if [ -f /var/run/reboot-required ]; then
  echo
  echo "$script_name: Done."
  cat /var/run/reboot-required
  echo
  echo "Packages that requested reboot:"
  cat /var/run/reboot-required.pkgs
  echo
else
  echo
  echo "$script_name: Done."
  echo "No restart is required."
  echo
fi