Rubish

Rubish is a UNIX shell written entirely in Ruby. It parses and compiles shell syntax into Ruby code, which is then executed by the Ruby Virtual Machine. It aims for full Bash compatibility and offers deep integration with Ruby, allowing seamless mixing of shell commands and Ruby code, including the use of Ruby's advanced features like blocks, iterators, and libraries. Rubish supports features beyond standard Bash, such as Ruby expressions as conditions, Ruby method call syntax for commands, method chaining, Ruby iterator blocks, inline Ruby evaluation, Ruby array and regexp literals, lambda expressions, Ruby-style function definitions, custom Ruby prompts, and lazy loading for slow shell initializations. It also includes a restricted mode for executing untrusted scripts safely and offers Zsh compatibility. Rubish can be embedded in other Ruby programs and supports custom I/O backends and child-process pre-exec hooks.