rush - the really uninteractive shell

Rush is designed to run POSIX scripts, and run them fast. Think of it as a Rust dash.

I know that the name is overused, but it's too good to pass up.

// TODO:

• [X] Simple command execution ls -ltr
• [X] Pipes exa | grep cargo
• [X] Exit status logic ! false && ls || date
• [ ] Redirection
  • [X] File descriptor to another ls error 2>&1
  • [X] To/from file date > time.txt < Cargo.toml wc
  • [X] Appending >>
  • [X] Here-docs <<
  • [ ] Raw, non-io file descriptors 4>&7
• [ ] Async execution &
• [ ] Shell builtins
  • [ ] Normal built-ins
    • [ ] alias unalias
    • [X] cd
    • [ ] etc
  • [ ] Special built-ins
    • [X] exit
    • [ ] export
    • [ ] exec
    • [ ] etc
• [ ] Expansions
  • [X] Tilde expansion ls ~
  • [ ] Parameter expansion
    • [X] Basic expansion echo ${var:-other}
    • [ ] String length echo ${#var}
    • [ ] Suffix/prefix removal echo ${var%%pattern}
  • [X] Command substitution
  • [ ] Arithmetic expansion
• [X] Variables
• [X] Quotes
• [ ] IFS
• [ ] Functions
• [ ] Control flow if for while case etc
• [ ] Expand this to-do list

Decisions to make

• Should this shell replicate commands that are typically built-in but also have system alternatives?