Minecraft launcher

#!/bin/bash
LIBS=`find libraries/ -iname \*.jar | grep -v natives | xargs echo | sed 's/ /:/g'`
LAUNCHER="launcher.jar"
MAIN_CLASS=net.minecraft.client.main.Main
NATIVES=`find libraries/ -iname \*.jar | grep natives`
# Memory allocated to JVM
MEM=3072m
DIR="${PWD}"

function latest()
{
  VERS=`ls -v $1 | tail -n1 | sed 's/\.json//g'`;
  echo ${VERS}
}

VERSION=$(latest versions)
ASS_VER=$(latest assets/indexes)

MAIN_JAR=versions/${VERSION}/${VERSION}.jar
NAT_DIR="`find versions/${VERSION}/${VERSION}-natives-* -type d 2>/dev/null | tail -n 1`"
if [ "x" == "x${NAT_DIR}" ]; then
  NAT_DIR="versions/${VERSION}/${VERSION}-natives-`date +'%s'`"
fi

# Set username
if [ $# = 0 ]; then
  USER=Player;
else
  USER=$1;
fi

if [ ! -d ${NAT_DIR} ]; then
  mkdir -p ${NAT_DIR}
  for f in ${NATIVES}; do
    unzip -qq -o $f -x META-INF/* -d ${NAT_DIR};
  done;
fi

# Generate plausible UUID
# This is not required, but just looks good
UUID=`uuidgen -t`

# Let's run
echo "Starting Minecraft ${VERSION}..."
echo "Player ${USER}, assets ${ASS_VER}"
java -cp ${LIBS}:${MAIN_JAR} -Xmx${MEM} -Xms${MEM} \
  -Djava.library.path=${NAT_DIR} ${MAIN_CLASS} \
  --version ${VERSION} \
  --username ${USER} \
  --gameDir ${DIR} \
  --assetsDir ${DIR}/assets \
  --assetIndex ${ASS_VER} \
  --uuid ${UUID} \
  --accessToken null \
  --userProperties {} \
  --userType legacy #> /dev/null