Minecraft Server Luancher (with update check)

#!/usr/bin/env bash

#############################################################################
# MINECRAFT SERVER LAUNCHER
###########################
#
# This is a rather basic server launcher that gets the HTTP Headers for the
# minecraft server jar file and compares the Last-Modified header with a
# local copy of the header. If these values are different the script
# downloads a new version of the server jar. It then updates the local
# copy of the header value.
#
#############################################################################
# HELP:
###########################
#
# ./launcher.bash
#    Runs the version check only
#
# ./laucnher.bash start
#    Runs the version check and then starts the server with the defaults
#
# ./launcher.bash start="parms"
#    Runs the version check and then starts the server with the 'params'
#
# ./launcher.bash path="path"
#    Starts by changing the directory to 'path' and runs the version check
#
# ./launcher.bash archive
#    If the checksums are difference, archive the world before existing
#
#############################################################################
# LICENCE
###########################
#
# Copyright 2011 Nicholas Steicke. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without modification, are
# permitted provided that the following conditions are met:
#
#    1. Redistributions of source code must retain the above copyright notice, this list of
#       conditions and the following disclaimer.
#
#    2. Redistributions in binary form must reproduce the above copyright notice, this list
#       of conditions and the following disclaimer in the documentation and/or other materials
#       provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY NICHOLAS STEICKE ''AS IS'' AND ANY EXPRESS OR IMPLIED
# WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
# FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NICHOLAS STEICKE OR
# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
# ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
# ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
# The views and conclusions contained in the software and documentation are those of the
# authors and should not be interpreted as representing official policies, either expressed
# or implied, of Nicholas Steicke.

which="/usr/bin/which"

rm=`$which rm`
ln=`$which ln`
touch=`$which touch`
cat=`$which cat`
curl=`$which curl`
grep=`$which grep`
sed=`$which sed`
java=`$which java`
sha1sum=`$which sha1sum`
tar=`$which tar`
mkdir=`which mkdir`

python=`$which python`

SERVER_URL="https://s3.amazonaws.com/MinecraftDownload/launcher/minecraft_server.jar"

WDIR="."
START=false
START_PARAMS="-Xmx1024M -Xms1024M"
ARCHIVE=false

while [ $# -ne 0 ]; do
  if [[ ${1:0:5} == "path=" ]]; then
    WDIR=${1:5}
  elif [[ ${1:0:5} == "start" ]]; then
    START=true
    if [[ ${1:5} != "" ]]; then
      START_PARAMS=${1:5}
    fi
  elif [[ $1 == "archive" ]]; then
    ARCHIVE=true
  fi
  shift
done

cd $WDIR
echo -n "Working in "
pwd

$touch .mclancher_lastmodified

CURVERSION=`$cat .mclancher_lastmodified`

echo "Checking HTTP Headers to see if their version is different..."

$curl -sIL $SERVER_URL > /tmp/mclauncher

VERSION=`$grep 'Last-Modified: ' /tmp/mclauncher | $sed 's/^Last-Modified: \([a-zA-Z0-9,: ]*\).*$/\1/'`

if [[ $python == "" ]]; then
  COMPAT_VERSION=`echo -n $VERSION | $sed 's/ /_/g' | $sed 's/:/./g'`
  COMPAT_CURVERSION=`echo -n $CURVERSION | $sed 's/ /_/g' | $sed 's/:/./g'`
else
  COMPAT_VERSION=`$python -c "from datetime import datetime; print datetime.strptime('$VERSION', '%a, %d %b %Y %H:%M:%S %Z').strftime('%Y-%m-%dT%H.%I.%S')"`
  COMPAT_CURVERSION=`$python -c "from datetime import datetime; print datetime.strptime('$CURVERSION', '%a, %d %b %Y %H:%M:%S %Z').strftime('%Y-%m-%dT%H.%I.%S')"`
fi

$rm /tmp/mclauncher

if [[ $VERSION != $CURVERSION ]] || [ ! -f minecraft_server.jar ]; then
  if [ -f minecraft_Server.jar ]; then
    echo "The server has been modified! Lets get it!"
  else
    echo "There is no minecraft_server.jar, so lets get one!"
  fi

  echo -n $VERSION > .mclancher_lastmodified

  $curl $SERVER_URL -so minecraft_server_$COMPAT_VERSION.jar

  $sha1sum minecraft_server_$COMPAT_VERSION.jar > minecraft_server_$COMPAT_VERSION.jar.sha1sum

  if [ -f minecraft_server.jar ]; then
    $rm minecraft_server.jar
  fi

  $ln -s minecraft_server_$COMPAT_VERSION.jar minecraft_server.jar
else
  echo "Already upto date."
fi

SUM=`$cat "minecraft_server_$COMPAT_VERSION.jar.sha1sum"`
CURSUM=`$cat "minecraft_server_$COMPAT_CURVERSION.jar.sha1sum"`

if [[ ${SUM:0:40} == ${CURSUM:0:40} ]]; then
  echo "The file is different, this was probably an update."

  if $ARCHIVE && [ -f server.properties ]; then
    WORLD=`$grep 'level-name' server.properties`
    WORLD=${WORLD:11}

    $mkdir -p backups

    $tar -cjf "backups/$WORLD.pre-$COMPAT_VERSION.tar.bz2" $WORLD

    echo 'Created world archive:'
    echo "  backups/$WORLD.pre-$COMPAT_VERSION.tar.bz2"
  fi
fi

if $START; then
  echo "Starting server..."
  exec $java $START_PARAMS -jar minecraft_server.jar nogui
fi