Ruby Install Minimal script for MacOS and Linux. You can use it to install a recent Ruby using `rbenv` and `ruby-build`, with Jemalloc & YJIT enabled. Run it like so: `bash -c "$(curl -fsSL https://bit.ly/ruby-install-0-2-1)" -- 3.4.1`

ruby-install

#!/usr/bin/env bash
# vim: ft=bash
#
# © 2025 Konstantin Gredeskoul <kig AT kig.re>
#   All rights reserved.
#   MIT License.
#
# This script uses rbenv/ruby-build to install Ruby on OS-X or Linux. It configures
# Ruby build flags in such a way to ensure Ruby is linked with libjemalloc (which
# reduces the memory by half) and YJIT enabled. It has been tested on both Linux and
# MacOS.
#
# The script has no dependencies on Bashmatic Library, and can be invoked and
# executed as a standalone script. This is why it also exists as a Github Gist:
# https://bit.ly/ruby-install-sh
#
# This allows running it directly from the command line and is the recommended way,
# eg to install Ruby 3.4.1 with YJIT and Jemalloc enabled:
#
#       bash -c "$(curl -fsSL https://bit.ly/ruby-install-0-2-1)" -- 3.4.1
#
# Or if you are comfortable using BASH alises, you can add this to your ~/.bashrc:
#
#       alias rb-install='bash -c "$(curl -fsSL https://bit.ly/ruby-install-0-2-1)" -- '
#
# And then, anytime you need a new Ruby installed, it just can't get any simpler than:
#
#       rb-install 3.4.1
#       rb-install 3.3.6
#
#──────────────────────────────────────────────────────────────────────────────────
# NOTE: On Linux you might need to set either $RBENV_HOME or $RBENV_ROOT variables.
#
# NOTE: To pass additional flags to "rbenv install <version>" set the variable
#       $RBENV_INSTALL_FLAGS to the desired flags (default is -s). For example
#       you may want to keep the sources around in case the build failed, by
#       setting $RBENV_INSTALL_FLAGS="-k".
#
# USAGE:
#       # Argument overrides any other ruby version passing method
#       install-ruby 3.4.1
#
#       # if a file .ruby-version exists in the current directory, we install that version
#       install-ruby
#
#       # or if $RUBY_VERSION is defined
#       export RUBY_VERSION=3.5.5
#       install-ruby
#────────────────────────────────────────────────────────────────────────────────────────────────────────
#   
# This block here work on ZSH and BASH. It attempts to determine 
# whether you ran "source dev" to get access to the BASH functions
# defined therein; OR you ran "./dev" to get the application started
# in a subshell. The __run_as_script variable is set to 1 in the case
# when the script is ran, not sourced, and zero otherwise.
# 
if [[ -n ${ZSH_EVAL_CONTEXT} && ${ZSH_EVAL_CONTEXT} =~ :file$ ]] ||
  [[ -n $BASH_VERSION && $0 != "${BASH_SOURCE[0]}" ]] ; then
  export __run_as_script=0 2>/dev/null
else
  export __run_as_script=1 2>/dev/null
fi

# shellcheck disable=SC2086

export txtblk='\e[0;30m'  # Black - Regular
export txtred='\e[0;31m'  # Red
export txtgrn='\e[0;32m'  # Green
export txtylw='\e[0;33m'  # Yellow
export txtblu='\e[0;34m'  # Blue
export txtpur='\e[0;35m'  # Purple
export txtcyn='\e[0;36m'  # Cyan
export txtwht='\e[0;37m'  # White
export errclr='\e[0;101m' # White on red
export bold='\e[1m'       # Text Reset
export clr='\e[0m'        # Text Reset

export SCRIPT_VERSION="0.2.1"
export OS="$(uname -s | tr '[:upper:]' '[:lower:]')"

line() { echo "────────────────────────────────────────────────────────────────────────────────────────────────────────"; }
now() { date '+%F.%T.%S   ' | tr -d '\:\-\.'; }
version() { echo -e "${txtylw}v$SCRIPT_VERSION${clr}"; }
inf() { echo -e "${txtgrn}${bold}──────────────────────────┤ $(printf '%s' "$*") ${clr}"; }

function ts()   { echo -n "$(date '+%H:%M:%S') ${txtpur}ruby-install${clr}     | "; }
function inf_() { echo -n -e "${txtblu}$(ts)${txtcyn}$*${clr}"; }
function inf() { inf_ "$@"; echo; }
function fnc() { echo -e "${txtblu}$(ts)${txtylw}$(shift)$*${clr}";  }
function wrn() { echo -e "${txtylw}$(ts)${txtylw}$*${clr}"; }
function err() {
  echo -e "\n${txtred}$(ts)${txtred}💀  ${errclr}${bold}$*${clr}\n" >&2
}

# shellcheck disable=SC2120
function ok()   {
  echo -e "${txtgrn}${bold}${*:-"[ OK ]"}  ✅  ${clr}";
}
# shellcheck disable=SC2120
function fail() {
  echo -e "${txtred}${bold}${*:-"FAILED"}  ❌  ${clr}";
}
function puts() { echo -e "$*${clr}"; }

# shellcheck disable=SC2120
status-ok() {
  local msg="${*:-""}"
  echo -e "${txtgrn}${bold}[ ✔️ ]${clr}"
  [[ -n "$msg" ]] && echo -e " (INFO: $*)${clr}"
  echo
}
status-err() {
  echo -e -n "${txtred}${bold}[ ✖️ ] "
  [[ -n "$*" ]] && echo -e "(ERROR: $*)${clr}"
  echo
}

print() {
  echo -e "$@"
}

# Execute a command and show the result, and/or the output of the command.
function run_command() {
  inf_ "❯ ${green}$(printf '%-60.60s' "$*")  "
  set +e

  # Run the command
  if is-verbose; then
    echo
    eval "$*"
  else
    eval "$*" >/dev/null 2>&1
  fi

  local code=$?
  ((__run_as_script)) && set -e


  if [[ ${code} -eq 0 ]]; then
    ok
  else
    fail
  fi

  return ${code}
}
  

header() {
  line
  print "\
${txtgrn}Ruby Installer Script | Version $(version)${txtgrn} ${OS^} ($(arch))
    ${txtblu} 

${txtgrn}DESCRIPTION:${txtblu}
  A BASH script that automates installation and building of the Ruby Interpreter
  using rbenv and ruby-bulid, with YJIT enabled, linked with libjemalloc, 
  as well as OpenSSL and libyaml.

  Supported Operating Systems: Linux (Ubuntu) and MacOS (tested on Sequoia).

  © 2025 Konstantin Gredeskoul, https://kig.re/, @kigster on Github.${clr}
  "
  line
}

usage() {
  local executable="ruby-install"
  print "
${txtgrn}NAME:
  ${txtylw}install-ruby

${txtgrn}USAGE:
  ${txtylw}${executable} [ ruby-version ] ${clr} # install Ruby Version pass as argument
  ${txtylw}${executable}                  ${clr} # install Ruby Version from .ruby-version file

  ${txtylw}export RUBY_VERSION=3.4.1 
  ${txtylw}${executable}                  ${clr} # Install Ruby using the env variable as a version.

${txtgrn}ONLINE USAGE:
  ${txtylw}bash -c \"\$(curl -fsSL https://bit.ly/ruby-install-$(echo "${SCRIPT_VERSION}" | sed 's/[.]/-/g'))\" -- 3.4.1${clr}
"
  line
  exit 0
}

declare NOW

function parse-args() {
  NOW="$(now | tr -d '\n ')"
  export NOW

  if [[ $* =~ (-h|--help) ]]; then
    header
    usage
  fi
}

function configure() {
  fnc "Identifying the Ruby Version to install..."
  export RUBY_VERSION_ARG="$1"
  export DEFAULT_RUBY_VERSION="${DEFAULT_RUBY_VERSION:-"3.4.1"}"
  export RUBY_FILE_VERSION="${RUBY_VERSION:-"$(test -f .ruby-version && cat .ruby-version)"}"
  export RBENV_INSTALL_FLAGS="$RBENV_INSTALL_FLAGS --skip-existing"

  if [[ $RUBY_VERSION_ARG =~ ([0-9]+.[0-9]+) ]]; then
    export RUBY_VERSION=$RUBY_VERSION_ARG
  fi

  export RUBY_VERSION="${RUBY_VERSION:-${RUBY_FILE_VERSION:-${DEFAULT_RUBY_VERSION}}}"
  echo -e "${txtpur}RUBY Version to Install   : ${txtcyn}${RUBY_VERSION}"

  declare SUDO

  if [[ $OS =~ darwin ]]; then
    export RUBY_CFLAGS="-Wno-error=implicit-function-declaration"
    export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES
    export PACKAGES="rbenv jemalloc"

    export SUDO=false
    export INSTALLER="brew"
    export INSTALLER_FLAGS=" --quiet "

    export INSTALL_COMMAND="install"
    export UNINSTALL_COMMAND="uninstall"
  else
    export PACKAGES="rbenv libjemalloc2"

    export SUDO=true
    export INSTALLER="apt-get"
    export INSTALLER_FLAGS=" -yqq --silent "

    export INSTALL_COMMAND="install"
    export UNINSTALL_COMMAND="remove"
  fi

  export SUDO_PREFIX=""
  [[ $SUDO == true ]] && export SUDO_PREFIX="sudo "

  export RBENV_ROOT="${RBENV_ROOT-"${RBENV_HOME:-"${HOME}/.rbenv"}"}"

  [[ -n $RBENV_ROOT && ! -d $RBENV_ROOT ]] && mkdir -p "$RBENV_ROOT"

  export OPT_DIR=$(if [[ -d /opt/homebrew ]]; then echo /opt/homebrew; else echo /usr/local; fi)
  export RUBY_CONFIGURE_OPTS="--with-jemalloc --enable-yjit --with-opt-dir=${OPT_DIR}"
  export RUBY_YJIT_ENABLE=1

  # rustc --version | awk '{print $2}' | tr '.' '0'
  export MIN_RUSTC_VERSION=108300
}

function version-integer() {
  echo "$1" | awk '{print $2}' | sed 's/[._]/0/g'
}

function rust-check() {
  inf "Rust Compiler installation and version check..."
  if [[ -x "$(command -v rustc)" ]]; then
    local rust_version
    rust_version="$(version-integer "$(rustc --version)" )"
    if [[ $rust_version -lt $MIN_RUSTC_VERSION ]]; then
      echo "Rust compiler is installed, but the version is older — $(rustc --version)."
      echo "Removing and reinstalling..."
      rust-reinstall
    else
      echo "Rust compiler is installed and is up to date."
    fi
  else
    echo "Rust compiler is not installed. Installing..."
    rust-reinstall
  fi
}

# OS-independent rustc reinstaller
function rust-reinstall() {
  inf "(Re)-Installing Rust compiler..."

  [[ -x "$(command -v rustup)" ]] && rustup default stable
  
  eval "${SUDO_PREFIX} ${INSTALLER} ${UNINSTALL_COMMAND} rustc ${INSTALLER_FLAGS} 2>/dev/null 1>&2 || true"
  eval "${SUDO_PREFIX} ${INSTALLER} ${UNINSTALL_COMMAND} rust  ${INSTALLER_FLAGS} 2>/dev/null 1>&2 || true"
  hash -r >/dev/null 2>&1 || true

  echo -e "${txtpur}System Package Installer  : ${txtcyn}${INSTALLER}"
  echo -n -e "${txtpur}Installing Rustup         : "

  export RUSTUP_INIT_SKIP_PATH_CHECK=yes
  ( curl -fsSL https://sh.rustup.rs | sh -s -- -y ) >/dev/null 2>&1
  local install_result=$?

  if [[ $install_result -ne 0 ]]; then
    status-err "Rustup installation failed with status ${install_result}"
    exit $install_result
  else
    status-ok
  fi

  # shellcheck disable=SC1091
  [[ -s "${HOME}/.cargo/env" ]] && source "${HOME}/.cargo/env"

  rustup default stable
}

function pre-install-darwin() {
  if [[ ! -x "$(command -v brew)" ]]; then
    inf "Installing Homebrew as none were found..."
    echo "Installing Homebrew..."
    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
  fi
}

# function pre-install-linux() {
#   # linux specific installation steps
# }

function pre-install() {
  # Invoke pre-installer
  pre_install_function="pre-install-${OS}"
  [[ -n "$(type -t "${pre_install_function}")" && "$(type -t "${pre_install_function}")" == "function" ]] && eval "${pre_install_function}"

  rust-check
}

function print-configuration() {
  line
  inf "Install Configuration:"
  inf " "
  inf "${txtpur}System Package Installer  : ${txtcyn}${INSTALLER}"
  inf "${txtpur}Installer Flags           : ${txtcyn}${INSTALLER_FLAGS}"
  inf "${txtpur}Packages To Install       : ${txtcyn}${PACKAGES}"
  line
  inf "${txtpur}RustC Compiler            : ${txtcyn}$(which rustc)"
  inf "${txtpur}RustC Version             : ${txtcyn}$(rustc --version)"
  inf "${txtpur}RUBY YJIT Enabled?        : ${txtcyn}$([[ $RUBY_CONFIGURE_OPTS =~ enable-yjit ]] && echo 'YES' || echo 'NO')"
  inf "${txtpur}RBENV ROOT                : ${txtcyn}${RBENV_ROOT}"
  inf "${txtpur}RUBY_CONFIGURE_OPTS       : ${txtcyn}${RUBY_CONFIGURE_OPTS}"
  [[ -n $RUBY_CFLAGS ]] && \
    inf "${txtpur}RUBY_CFLAGS               : ${txtcyn}${RUBY_CFLAGS}${clr}"
  echo
  line
}

declare SUDO_PREFIX

function installer-update() {
  eval "${SUDO_PREFIX} ${INSTALLER} update ${INSTALLER_FLAGS} >/dev/null || true"
}

function rbenv-update() {
  command -V rbenv >/dev/null || {
    inf "Installing rbenv..."
    eval "${SUDO_PREFIX} ${INSTALLER} install ${INSTALLER_FLAGS} rbenv"
  }

  export RBENV_ROOT=${RBENV_ROOT:-$(rbenv --prefix)}
  [[ -d $RBENV_ROOT/plugins ]] || mkdir -p "${RBENV_ROOT}/plugins"

  # Perform this update in a sub-shell
  (
    cd "${RBENV_ROOT}/plugins"
    inf "Updating ruby-build..."
    [[ -d ruby-build ]] || git clone https://github.com/rbenv/ruby-build.git >/dev/null
    cd ruby-build && git pull
  )

  export PATH="$RBENV_ROOT/bin:$RBENV_ROOT/shims:$PATH"
}

function packages-install() {
  eval "${SUDO_PREFIX} ${INSTALLER} ${INSTALL_COMMAND} ${INSTALLER_FLAGS} ${PACKAGES} || true"
}

function install-ruby() {
  set +e
  local SH
  SH="$(basename "${SHELL}")"

  # Initialize rbenv
  eval "$(rbenv init - "${SH}")"

  line
  echo
  inf "Installing Ruby (using -s flag, i.e. skipping existing.)"
  inf "If you need to overwrite an existing installation, please"
  inf "uninstall it using first using the command ${txtylw}rbenv uninstall <version>${clr}"
  inf " "
  inf "${clr}❯ ${txtylw}rbenv install -s ${RUBY_VERSION}${clr}\n"
  inf "${txtpur} ⏳  Please wait while your Ruby is being cooked...${clr}\n"

  output="/tmp/ruby-$RUBY_VERSION/build"
  mkdir -p "$output"
  set +e
  rbenv install -s "${RUBY_VERSION}" 1>"${output}"/"${NOW}".stdout 2>"${output}"/"${NOW}".stderr
  status=$?

  if [[ $status -ne 0 ]]; then
    line
    echo -e "${errclr}ERROR   : → Ruby ${RUBY_VERSION} installation has failed with status ${status}.${clr}"
    sleep 0.5

    [[ -s ${output}/${NOW}.stdout ]] && cp "${output}/${NOW}.stdout" .
    [[ -s ${output}/${NOW}.stderr ]] && cp "${output}/${NOW}.stderr" .

    [[ -s ${NOW}.stderr ]] && {
      err "${txtred}Standard Error:${clr}"
      echo -e "${txtred}"
      line
      cat "${NOW}.stderr"
      echo -e "${clr}"
    }

    [[ -s ${NOW}.output ]] && {
      inf "${txtcyn}NOTE    : → Standard Output is available in the file ${txtylw}${NOW}.output${clr}"
    }

    [[ -s ${NOW}.stderr || -s ${NOW}.stdout ]] || {
      wrn "${txtylw}WARNING : → No STDOUT or STDERR was generated.${clr}"
    }
    inf "${txtgrn}HINT    : → Set env variable RBENV_INSTALL_FLAGS=-k to keep Ruby Source code around.${clr}\n"
    exit $status
  else
    line
    inf "${bold}${txtgrn}SUCCESS : → Ruby ${RUBY_VERSION} installed successfully.${clr}"
    line
    echo
  fi

  rbenv global "${RUBY_VERSION}"
  echo "RBENV Status about currently install versions:"
  rbenv versions
  echo
  line
}

declare temp_dir

function handle-ruby-version() {
  # Handle local .ruby-version
  if [[ -s .ruby-version ]]; then
    temp_dir=$(mktemp -d)
    export temp_dir
    mv -v .ruby-version "${temp_dir}/"
  fi
}

function print-post-install-status() {
  # Print the final results of the installation.
  echo -e "${txtylw}Ruby $RUBY_VERSION Build, Platform, Architecture, YJIT:"
  echo -e "  ${txtgrn}$(ruby --version)${clr}\n"

  echo -e "${txtylw}Configure Flags:"
  echo -e "${txtgrn}$(ruby -e 'puts RbConfig::CONFIG["configure_args"].strip' | tr -d '"' | tr -d "'" | sed 's/^\s*//g' | fold -w 60 -s | sed 's/^/  /g')\e[0m\n"

  echo -e "${txtylw}Linked Libraries:"
  echo -e "  ${txtgrn}$(ruby -e 'pp RbConfig::CONFIG["MAINLIBS"]' | tr -d '"')\e[0m\n"

  # Restore .ruby-version in the current directory if it were moved.
  if [[ -n $temp_dir && -d $temp_dir && -s $temp_dir/.ruby-version ]]; then
    mv -v $temp_dir/.ruby-version .
  fi
}

main() {
  fnc "parse-args($*)"
  parse-args "$@"
  fnc "header()"
  header
  fnc "configure($*)"
  configure "$@"
  fnc "pre-install()"
  pre-install
  fnc "installer-update()"
  installer-update
  fnc "rbenv-update()"
  rbenv-update
  fnc "packages-install()"
  packages-install
  fnc "print-configuration()"
  print-configuration
  fnc "handle-ruby-version()"
  handle-ruby-version
  fnc "install-ruby()"
  install-ruby
  fnc "print-post-install-status()"
  print-post-install-status
}

main "$@"

Installation on Ubuntu 20.04: