EsoRex is the ESO Recipe Execution Tool. It can list, configure and execute CPL-based recipes from the command line. One of the features provided by the CPL is the ability to create data-reduction algorithms that run as plugins (dynamic libraries). These are called recipes and are one of the main aspects of the CPL data-reduction development environment. As these recipes are dynamic libraries, it is not possible to run them directly from the command line. However, ESO provides several tools to do this, thus saving recipe developers the need to write such an application themselves. One of these is GASGANO (a GUI-based tool) and the other is EsoRex (which runs from the command line.