A Bash script to install Ruby, using rbenv/ruby-build, on Ubuntu/Debian and derivatives

install_ruby.sh

#!/bin/bash

# ------------------------------------------------------------------------------------------------
# Installs Ruby using rbenv/ruby-build - can be used multiple times, to install different versions
#
# Download and run locally:
#   wget git.io/inst_ruby -O install_ruby.sh && chmod a+x install_ruby.sh
#   ./install_ruby.sh 2.6.6
#
# Run from the web:
#   bash <(curl -sL git.io/inst_ruby) 2.6.6
#
# Based on blacktm's script, found here:
#   https://gist.github.com/blacktm/8302741
# Modified / updated by Dave Thwaites:
#   https://gist.github.com/DaveThw/7d9cf5c7922df0eaa4fc10c51b979b8d
# ------------------------------------------------------------------------------------------------

if [[ "x$1" == "x" ]]; then
  if [[ "${0:0:8}" == "/dev/fd/" ]]; then
    # URL=https://gist.github.com/DaveThw/7d9cf5c7922df0eaa4fc10c51b979b8d/raw/install_ruby.sh
    URL=git.io/inst_ruby
    echo "Usage: bash <(curl -sL $URL) <version>"
    echo "eg:"
    echo "  bash <(curl -sL $URL) 2.6.6"
    echo "or"
    echo "  bash <(curl -sL $URL) 2.7.1"
  else
    echo "Usage: $0 <version>"
    echo "eg '$0 2.6.6' or '$0 2.7.1'"
  fi
  exit
else
  VER=$1
fi

# Welcome message
echo -e "
This will install Ruby $VER using rbenv/ruby-build.

It will likely take about 2 hours to compile on the original Raspberry Pi,
about 35 minutes on the second generation, and about 16 minutes on the third.
Or about 7 1/2 mins in GalliumOS on an HP Chromebook 14 ('Falco').\n"

# Prompt to continue
read -p "  Continue? (y/n) " ans
if [[ $ans != "y" ]]; then
  echo -e "\nQuitting...\n"
  exit
fi
echo

# Time the install process
START_TIME=$SECONDS

# update the list of packages available to install
sudo apt update

# Ensure git is installed
sudo apt install -y git

if [[ -d ~/.rbenv ]]; then
  echo "rbenv already installed - pull latest updates:"
  git -C ~/.rbenv pull
else
  # Check out rbenv into ~/.rbenv
  git clone https://github.com/rbenv/rbenv.git ~/.rbenv
fi

# Add ~/.rbenv/bin to $PATH, enable shims and autocompletion
read -d '' String <<"EOF"
# rbenv
export PATH="$HOME/.rbenv/bin:$PATH"
eval "$(rbenv init -)"
EOF

grep -q rbenv ~/.bashrc; if [[ "$?" = "0" ]]; then
  echo "rbenv already enabled in ~/.bashrc"
else
  # Save to ~/.bashrc
  echo -e "\n${String}" >> ~/.bashrc
fi

echo "$PATH" | grep -q "/.rbenv/bin:"; if [[ "$?" = "0" ]]; then
  echo "rbenv already enabled in current shell"
  RBENV_ENABLED=yes
else
  RBENV_ENABLED=no
  # Enable rbenv for current shell
  eval "${String}"
fi;

if [[ -d ~/.rbenv/plugins/ruby-build ]]; then
  echo "ruby-build already installed - pull latest updates:"
  git -C ~/.rbenv/plugins/ruby-build pull
else
  # Install ruby-build as an rbenv plugin, adds `rbenv install` command
  git clone https://github.com/rbenv/ruby-build.git ~/.rbenv/plugins/ruby-build
fi

# Install ruby-build dependencies
#  See: https://github.com/rbenv/ruby-build/wiki#suggested-build-environment
sudo apt install -y autoconf bison build-essential libssl-dev libyaml-dev libreadline6-dev zlib1g-dev libncurses5-dev libffi-dev libgdbm-dev
# try to install libgdbm5 (may not work on all systems, eg Raspbery Pi)
sudo apt install -y libgdbm5
# if that fails, install libgdbm3
if [[ $? != 0 ]]; then sudo apt install -y libgdbm3; fi

# Install Ruby ($VER), don't generate RDoc to save lots of time
CONFIGURE_OPTS="--disable-install-doc --enable-shared" rbenv install $VER --verbose

# Set Ruby $VER as the global default
rbenv global $VER

# List available versions, if more than one:
if [[ $(rbenv versions | wc -l) > 1 ]]; then
  echo -e "\nAvailable versions of Ruby:"
  rbenv versions
fi

# Don't install docs for gems (saves lots of time)
if [[ -e ~/.gemrc ]]; then
  grep -q "gem: --no-document" ~/.gemrc; if [[ "$?" != "0" ]]; then
    # ~/.gemrc exists, but doesn't contain this line:
    echo "gem: --no-document" >> ~/.gemrc
  fi
else
  # ~/.gemrc doesn't exist:
  echo "gem: --no-document" > ~/.gemrc
fi

if [[ "$RBENV_ENABLED" = "no" ]]; then
  # Reminder to reload the shell
  echo -e "\nQuit and reload the current shell to get access to Ruby and rbenv."
  echo "Or, if you want to keep this shell open, re-load your .bashrc file, with:"
  echo "  source ~/.bashrc"
fi

# Print the time elapsed
ELAPSED_TIME=$(($SECONDS - $START_TIME))
echo -e "\nFinished in $(($ELAPSED_TIME/60/60)) hr, $(($ELAPSED_TIME/60%60)) min, and $(($ELAPSED_TIME%60)) sec\n"