Guard
Guard is a command line tool to easily handle events on file system
...To install for older versions, update Bundler at least 1.12: gem update bundler and Bundler should correctly resolve to earlier gems for your given Ruby version. Guard automates various tasks by running custom rules whenever file or directories are modified. It's frequently used by software developers, web designers, writers and other specialists to avoid mundane, repetitive actions and commands such as "relaunching" tools after changing source files or configurations. Common use cases include: an IDE replacement, web development tools, designing "smart" and "responsive" build systems/workflows, automating various project tasks and installing/monitoring various system services.