There are times when you need Unix shell, usually for one-off script or quick test. Here are ways I found to run shell on Chromebook, Android phone, and Windows.

• Chromebook
  1. Chrome Shell – Type <Ctrl-Alt-T> from Chrome browser or desktop to get “crosh>” command prompt, and then type shell to get a full Bash shell. You have to enable Developer Mode to get access to the shell command. Chromebook can be switched into Developer Mode by pressing <Esc-Refresh-Power> and then follow instructions.
  2. Crouton – Install crouton in developer mode. It's a shell script that installs Ubuntu/Debian in chroot environment, so you can switch between Chrome OS and Ubuntu/Debian.
     • Install Ubuntu on a Chromebook
     • Chromium OS Universal Chroot Environment

• Android
  1. Termux – Install from Play Store. It's Ubuntu-like command-line distro.
     • Termux

• Windows
  1. BusyBox – There is a BusyBox binary compiled for 32-bit and 64-bit Windows.
     • BusyBox for Windows
  2. Cygwin – Collection of Unix utilities running natively on Windows.
     • Cygwin
  3. Windows Subsystem for Linux (used to be called Bash on Ubuntu on Windows) – Go to Control Panel > Programs > Turn Windows features on or off, and enable the Windows Subsystem for Linux option. After reboot, download and install Ubuntu from Windows Store.
     • Windows Subsystem for Linux Documentation
  4. VirtualBox (or VMware or Hyper-V) – Full VM where you can install any Linux distro.
     • Oracle VM VirtualBox
  5. Git Bash – It's part of Git for Windows application.
     • Git for Windows