Updates the lwjgl that minecraft uses.

update_lwjgl.sh

#!/usr/bin/env bash

echo "Determining OS..."

if [[ "$(uname -s)" == "Linux" ]]; then
    mcdir="$HOME/.minecraft/"
    downloader="wget --no-check-certificate -q -O"
    os="linux"
    natives="libjinput-linux libjinput-linux64 liblwjgl liblwjgl64 libopenal libopenal64"
elif [[ "$(uname -s)" == "Darwin" ]]; then
    mcdir="$HOME/Library/Application\ Support/minecraft/"
    downloader="curl -o"
    os="macosx"
    natives="libjinput-osx.jnilib liblwjgl.jnilib openal.dylib"
else
    echo "OS not supported.  Exploding..."
    exit 1
fi

echo "Determining installed LWJGL version..."

installed="$(unzip -p $mcdir/bin/lwjgl.jar | strings | grep  '^[0-9]*\.[0-9]*\.[0-9]*')"

echo "LWJGL $installed installed"

echo "Determining latest online version..."

latest=$(${downloader%%-o} - http://lwjgl.org/download.php |\
        grep -oE  "https?:\/\/sourceforge.net\/projects\/java-game-lib\/files\/Official%20Releases\/LWJGL%20[0-9|\.]*")

echo "Found version ${latest##*%20}"

if [[ "${latest##*%20}" == "$installed" ]]; then
    echo "LWJGL already at current version."
    if [[ "$1" == "-force" ]]; then
        echo "Updating anyways..."
    else
        exit 0
    fi
fi

echo "Determining download URL..."

dlurl=$(${downloader%%-o} - "$latest" |\
        grep -oE -m1 "https?://sourceforge.net/projects/java-game-lib/files/Official%20Releases/LWJGL%20[0-9|\.]*/lwjgl-[0-9|\.]*.zip")

echo "Checking if ~./cache/ exists..."

if [[ ! -d "$HOME/.cache/" ]]; then
    echo "~/.cache/ did not exist.  Creating..."
    mkdir "$HOME/.cache/"
fi

echo "Downloading latest LWJGL..."

$downloader "$HOME/.cache/lwjgl.zip" "$dlurl"

echo "Extracting zip file..."

unzip -qqo "$HOME/.cache/lwjgl.zip" -d "$HOME/.cache/"

lwjgldir=$(find -L "$HOME/.cache" -maxdepth 1 -type d -name "*lwjgl*" -print)
echo "Copying files..."

for i in "jinput" "lwjgl" "lwjgl_util"; do
    echo "Copying $i..."
    cp "$lwjgldir/jar/$i.jar" "$mcdir/bin/"
done
for i in $natives; do
    echo "Copying $i..."
    cp "$lwjgldir/native/$os/$i.so" "$mcdir/bin/natives/"
done

echo "Deleting cache..."

rm -rf "$lwjgldir"

Updated your script

• fix no longer working URLs
• Removed grep dependency
• Added check for unzip availability
• Hardened code style
  TODO: check download and unzip success and exit with error message if it fail

#!/usr/bin/env bash

# Exit on error. Append "|| true" if you expect an error.
set -o errexit
# Exit on error inside any functions or subshells.
set -o errtrace
# Do not overwrite an existing file with the >, >&, and <> redirection operators.
set -o noclobber
# Do not allow use of undefined vars. Use ${VAR:-} to use an undefined VAR
set -o nounset
# Pipeline's return status is the value of the last (rightmost) command
# to exit with a non-zero status, or zero if all commands exit successfully.
set -o pipefail

if ! which unzip; then
  echo >&2 "the 'unzip' utility is required!"
  exit 1
fi

echo 'Determining OS...'

declare __unames
__unames="$(uname -s)"
declare __mcdir
declare __os
declare __downloader
declare -a __natives
if [[ "${__unames}" == "Linux" ]]; then
  __mcdir="${HOME}/.minecraft/"
  __downloader='wget --no-check-certificate -q -O'
  __os='linux'
  __natives=(
    'libjinput-linux'
    'libjinput-linux64'
    'liblwjgl'
    'liblwjgl64'
    'libopenal'
    'libopenal64'
  )
elif [[ "${__unames}" == "Darwin" ]]; then
  __mcdir="${HOME}/Library/Application Support/minecraft/"
  __downloader='curl -o'
  __os='macosx'
  __natives=(
    'libjinput-osx.jnilib'
    'liblwjgl.jnilib'
    'openal.dylib'
  )
else
  echo >&2 'OS not supported.  Exploding...'
  exit 1
fi

echo 'Determining installed LWJGL version...'

[[ "$(
  unzip -p "${__mcdir}/bin/lwjgl.jar" 'org/lwjgl/Sys.class' | strings
)" =~ [0-9]+\.[0-9]+\.[0-9]+ ]]
declare __installed="${BASH_REMATCH[0]}"

echo "LWJGL ${__installed} installed"

echo 'Determining latest online version...'

[[ "$(
  ${__downloader%%-o} - 'http://legacy.lwjgl.org/download.php.html'
)" =~ https?://sourceforge.net/projects/java-game-lib/files/Official%20Releases/LWJGL%20[0-9|\.]* ]]
declare __latest="${BASH_REMATCH[0]}"

echo "Found version ${__latest##*%20}"

if [[ "${__latest##*%20}" == "${__installed}" ]]; then
  echo >&2 'LWJGL already at current version.'
  if [[ "${1:-}" == "-force" ]]; then
    echo 'Updating anyways...'
  else
    exit 0
  fi
fi

echo 'Determining download URL...'

[[ "$(
  ${__downloader%%-o} - "${__latest}"
)" =~ https?://sourceforge.net/projects/java-game-lib/files/Official%20Releases/LWJGL%20[0-9|\.]*/lwjgl-[0-9|\.]*.zip ]]
declare __dlurl="${BASH_REMATCH[0]}"

echo "Checking if ${HOME}/.cache/ exists..."

if [[ ! -d "${HOME}/.cache/" ]]; then
  echo "${HOME}/.cache/ did not exist.  Creating..."
  mkdir "${HOME}/.cache/"
fi

echo 'Downloading latest LWJGL...'

${__downloader} "${HOME}/.cache/lwjgl.zip" "${__dlurl}"

echo 'Extracting zip file...'

unzip -qqo "${HOME}/.cache/lwjgl.zip" -d "${HOME}/.cache/"

declare __lwjgldir
__lwjgldir="$(find -L "${HOME}/.cache" -maxdepth 1 -type d -name "*lwjgl*" -print)"
echo 'Copying files...'

for i in 'jinput' 'lwjgl' 'lwjgl_util'; do
  echo "Copying ${i}..."
  cp "${__lwjgldir}/jar/${i}.jar" "${__mcdir}/bin/"
done
for i in "${__natives[@]}"; do
  echo "Copying ${i}..."
  cp "${__lwjgldir}/native/${__os}/${i}.so" "${__mcdir}/bin/natives/"
done

echo 'Deleting cache...'

find "${__lwjgldir}" -delete