Detect if MRI Ruby is built with jemalloc library or not, download with `curl -fSL http://bit.ly/ruby-jemalloc-check > ruby-jemalloc-check.sh`

ruby-jemalloc-check.sh

#!/usr/bin/env bash
# vi: ft=sh
#
# https://gist.github.com/kigster/8ddebf9fddff25620e64d558dd4d56b7
#
# © 2019-2022 Konstantin Gredeskoul, Inc., All rights reserved.
# MIT LICENSE
# ————————————————————————————————————————————————————————————————
# This script verifies that the ruby interpreter (either the one in
# the $PATH, or the one specified by the -r / --ruby option) is linked
# with jemalloc library for efficient memory utilization.
#
# It works well on Linux and Mac OSX.
#
# BACKGROUND
# ————————————————————————————————————————————————————————————————
# Ruby versions 2.5 and earlier had a simpler method, typically
# running the following command and expecting the output to
# contain something like '-ljemalloc -lm ... '
#
#     ruby -r rbconfig -e "puts RbConfig.CONFIG['LIBS']"
#
# Unfortunately, this method no longer works with Ruby 2.6
# and later, nor did it ever work with Linux.
#
# For this reason, the following script is provided to verify
# if your Ruby is using jemalloc memory allocator or not.
#
# USAGE:
#   curl -fSL http://bit.ly/ruby-jemalloc-check > ruby-jemalloc-check.sh
#   chmod 755 ruby-jemalloc-check.sh
#
#   ./ruby-jemalloc-check.sh --help
#   ./ruby-jemalloc-check.sh -r /usr/bin/ruby
#
# ————————————————————————————————————————————————————————————————

set +e

export jm_option_ruby=$(command -v ruby 2>/dev/null)
export jm_option_quiet=false

export jm_action_detect=false
export jm_action_stats=false
export jm_action_help=false

export color_red="\e[1;31m"
export color_green="\e[1;32m"
export color_yellow="\e[1;33m"
export color_blue="\e[1;34m"
export clr="\e[0m"

function jm.printf() {
  if "${jm_option_quiet}"; then
    echo >/dev/null
  else
    printf "$@"
  fi
}

# @description prints the info about current version of ruby
function jm.ruby.report() {
  jm.printf "${color_blue}Ruby version being tested:\n  →  ${color_yellow}${jm_option_ruby} ${color_blue}$(jm.ruby.describe)${clr}\n"
}

# @description Prints ruby version under test
function jm.ruby.describe() {
  ${jm_option_ruby} -e 'puts "#{RUBY_VERSION} (#{RUBY_PLATFORM})"'
  ${jm_option_ruby} -e 'puts "#{RUBY_VERSION} (#{RUBY_PLATFORM})"'
}

# @description detects jemalloc or exits
function js.jemalloc.detect-or-exit() {
  jm.jemalloc.detect-quiet || {
    jm.printf "${color_red}ERROR: No jemalloc detected in ruby ${jm_option_ruby}${clr}\n"
    exit 1
  }
}

# @description prints jemalloc statistics if jemalloc is available
function jm.jemalloc.stats() {
  js.jemalloc.detect-or-exit
  MALLOC_CONF=stats_print:true ${jm_option_ruby} -e "exit" 2>&1 | less -S
}

# @description returns 0 if jemalloc was detected or 1 otherwise
function jm.jemalloc.detect-quiet() {
  MALLOC_CONF=stats_print:true ${jm_option_ruby} -e "exit" 2>&1 | grep -q "jemalloc statistics"
}

# @description detects if jemalloc is linked and if so prints the info to output
function jm.jemalloc.detect-loud() {
  jm.printf "${color_blue}Checking if ruby ${color_yellow}${jm_option_ruby}${color_blue} is linked with jemalloc... \n"
  jm.printf "${color_yellow}$(jm.ruby.report)${clr}\n\n"
  jm.jemalloc.detect-quiet
  local code=$?
  if [[ ${code} -eq 0 ]]; then
    jm.printf " ✅ ${color_green} — jemalloc was detected.\n"
  else
    jm.printf " 🚫 ${color_red} — jemalloc was not detected.\n"
  fi
  jm.printf "${clr}\n"
  return ${code}
}

# @description Prints the help screen and exits
function usage() {
  jm.printf "
${color_green}USAGE:${clr}
  ${color_yellow}$(basename $0) [ options ]${clr}

${color_green}DESCRIPTION:${clr}
  This script verifies that a given ruby binary is linked with jemalloc,
  the optimized for defragmentation memory allocator, which is a drop-in
  replacement for libc malloc.

  The script has several actions:
    - check if the ruby binary is linked with jemalloc (-j/--jemalloc)
    - print jemalloc statistics if available (-s/--stats)
    - print this help screen (-h/--help)

${color_green}ACTIONS:${clr}
  -j/--jemalloc     Check if the ruby binary is linked with jemalloc
  -h/--help         This page (also printed when no arguments are provided)
  -s/--stats        Print the jemalloc stats (when linked with jemalloc)

${color_green}OPTIONS:${clr}
  -r/--ruby PATH    Path to the ruby binary to check (defaults to the
                    first ruby found in the \$PATH)

  -q/--quiet        Do not print output, exit with 1 if no jemalloc, or 0
                    if jemalloc was found.

"
  exit 0
}

if [[ -z $* ]]; then
  usage
fi

# Parse additional flags
while :; do
  case $1 in
    -d | --detect)
      shift
      export jm_action_detect=true
      ;;
    -s | --stats)
      shift
      export jm_action_stats=true
      ;;
    -h | -\? | --help)
      shift
      export jm_action_help=true
      ;;
    -q | --quiet)
      shift
      export jm_option_quiet=true
      ;;
    -r | --ruby)
      shift
      if [[ -x $1 && $(basename $1) == "ruby" ]]; then
        export jm_option_ruby="$1"
      else
        jm.printf "${color_red} Invalid ruby interpreter provided: $1${clr}\n"
        exit 1
      fi
      shift
      ;;
    --) # End of all options; anything after will be passed to the action function
      shift
      break
      ;;
    *)
      [[ -n $1 ]] && {
        jm.printf "${color_red}ERROR: invalid option: $1${clr}\n"
        exit 1
      }
      break
      ;;
  esac
done

if ${jm_action_help}; then
  usage
fi

jm.printf "${color_green}Using Ruby Binary: ${color_yelow}${jm_option_ruby}${clr}\n"

if ${jm_option_quiet}; then
  jm.jemalloc.detect-quiet
  exit $?
fi

if ${jm_action_detect}; then
  jm.jemalloc.detect-loud
  exit $?
fi

if ${jm_option_stats}; then
  jm.jemalloc.stats
  exit $?
fi