Complete installer for PiCrate (on Buster Raspbian) including jdk and jruby dependencies

buster_install.sh

#!/usr/bin/env bash
# Bash Script to install PiCrate and dependencies on Raspbian Buster
# JAVA_PATH="/opt/jdk13"
JAVA_PATH="/usr/lib/jvm/java-11-openjdk-armhf"
# JAVA_PATH="/usr/lib/jvm/java-11-openjdk-armhf"
JRUBY_VERSION="9.2.19.0"
MRI_RUBY="2.5.0"
JRUBY_PATH="/opt/jruby-${JRUBY_VERSION}"
GEM="${HOME}/.gem/ruby/${MRI_RUBY}"

function install_java {
  if [ -x "$(command -v java)" ]
  then
    java -version
  else
    local commands=(update upgrade)
    for cmd in "${commands[@]}"
    do # update before install
    sudo apt-get "${cmd}"
  done
  echo "Installing openjdk-8"
  sudo apt-get install openjdk-8-jdk
fi
}

install_java

function wget_jruby {
  wget "https://repo1.maven.org/maven2/org/jruby/jruby-dist/${JRUBY_VERSION}/jruby-dist-${JRUBY_VERSION}-bin.tar.gz"
  sudo tar xzvf "${HOME}/jruby-dist-${JRUBY_VERSION}-bin.tar.gz" -C /opt
  echo "Downloaded JRuby"
  if [[ (-n ${JAVA_HOME}) ]]
  then
    echo "JAVA_HOME=${JAVA_HOME}"
  else
    echo "export JAVA_HOME=${JAVA_PATH}" >> "${HOME}/.profile"
    export JAVA_HOME="${JAVA_PATH}"
    sudo ${JRUBY_PATH}/bin/jgem install jruby-launcher
    echo "Installed JRuby launcher"
    sync
  fi
}

wget_jruby

function install_jruby {
  local commands=(jruby jgem jirb)
  for cmd in "${commands[@]}"
  do
    sudo update-alternatives --install /usr/bin/"${cmd}" "${cmd}" "${JRUBY_PATH}/bin/${cmd}" 100
  done
}

install_jruby

function create_gem_home {
  if [[ (-n ${GEM_HOME}) ]]
  then
    echo "GEM_HOME=${GEM_HOME}"
  else
    mkdir -p "${GEM}"
    commands=(
    "GEM_HOME=${GEM}"
    "GEM_PATH=${GEM}"
    "PATH=\"\${GEM_PATH}/bin:\${PATH}\""
    )
    for cmd in "${commands[@]}"
    do
      echo "export ${cmd}" >> ~/.profile
    done
  fi
}

create_gem_home

function install_picrate {
  export GEM_HOME="${GEM}"
  export PATH="${GEM}"/bin:"${PATH}"
  jgem install rake
  jgem install picrate
}

install_picrate