Determine Active Operating System in Bash Script

active_os.sh

#!/usr/bin/env bash

# * Determine operating system via $OSTYPE
function active_operating_system_ostype() {
  echo
  echo "Determining active operating system via \$OSTYPE"
  echo " » \$OSTYPE output: $OSTYPE"

  local active_os

  if [[ "$OSTYPE" == "linux-gnu"* ]]; then
    active_os="Linux"

  elif [[ "$OSTYPE" == "darwin"* ]]; then
    active_os="MacOS"

  elif [[ "$OSTYPE" == "cygwin" ]]; then
    # * POSIX compatibility layer and Linux environment emulation for Windows
    active_os="Windows"

  elif [[ "$OSTYPE" == "msys" ]]; then
    # * Lightweight shell and GNU utilities compiled for Windows (part of MinGW)
    active_os="Windows"

  elif [[ "$OSTYPE" == "win32" ]]; then
    active_os="Windows"

  elif [[ "$OSTYPE" == "freebsd"* ]]; then
    active_os="FreeBSD"

  else
    active_os="Unknown"
  fi

  echo " ✔ Active Operating System: ${active_os}"
}

active_operating_system_ostype


# * Determine operating system using uname
function active_operating_system_uname() {
  local uname_output
  local active_os

  uname_output="$(uname -s)"

  echo
  echo "Determining active operating system via uname -s"
  echo " » uname output: $uname_output"

  case "${uname_output}" in
    Linux*)     active_os=Linux;;
    Darwin*)    active_os=MacOS;;
    CYGWIN*)    active_os=Cygwin;;
    MINGW*)     active_os=MinGw;;
    FreeBSD*)     active_os=FreeBSD;;
    *)          active_os="UNKNOWN:${uname_output}"
  esac

  echo " ✔ Active Operating System: ${active_os}"

  # * Linux
  if [[ "$active_os" == "Linux" ]]; then
    echo " » Executing Linux logic.."

  # * MacOS
  elif [[ "$active_os" == "MacOS" ]]; then
    echo " » Executing Mac logic.."

  else
    echo " » Unknown operating system.  Aborting."
    exit 1
  fi
}

active_operating_system_uname