Just for fun, looking at code count as a rough measure of complexity.

rubish: 26,842

rc (plan9 shell): 5,888

To be fair, rubish does a lot more than rc. rc is pretty minimal.

rc source:

https://github.com/9front/9front/tree/front/sys/src/cmd/rc

Measures below:

    $ wc -l `find . -name '*.rb'`
      1124 ./rubish/execution_context.rb
        43 ./rubish/frontend.rb
      260 ./rubish/builtins/hash_directories.rb
      510 ./rubish/builtins/echo_printf.rb
      834 ./rubish/builtins/bind_readline.rb
      182 ./rubish/builtins/directory_stack.rb
      299 ./rubish/builtins/read.rb
      324 ./rubish/builtins/trap.rb
      129 ./rubish/builtins/arithmetic.rb
      862 ./rubish/completion.rb
      988 ./rubish/expansion.rb
      431 ./rubish/completions/git.rb
      114 ./rubish/completions/ssh.rb
      530 ./rubish/completions/bash_helpers.rb
      453 ./rubish/completions/help_parser.rb
      167 ./rubish/ast.rb
        46 ./rubish/frontend/tty.rb
      1179 ./rubish/runtime.rb
      127 ./rubish/lazy_loader.rb
        63 ./rubish/data_define.rb
      1163 ./rubish/runtime/command.rb
      153 ./rubish/runtime/job.rb
      7270 ./rubish/runtime/builtins.rb
      306 ./rubish/config.rb
      2442 ./rubish/repl.rb
      1316 ./rubish/codegen.rb
      1180 ./rubish/lexer.rb
      742 ./rubish/history.rb
      1169 ./rubish/parser.rb
        67 ./rubish/startup_profiler.rb
      848 ./rubish/prompt.rb
        47 ./rubish/data/readline_config.rb
      716 ./rubish/data/builtin_help.rb
      251 ./rubish/data/shell_options.rb
        53 ./rubish/data/completion_data.rb
        5 ./rubish/version.rb
      248 ./rubish/shell_state.rb
      140 ./rubish/arithmetic.rb
        61 ./rubish.rb
    26842 total

    $ wc -l *.c *.h *.y
      547 code.c
    1173 exec.c
      234 getflags.c
      259 glob.c
      240 havefork.c
      137 here.c
      301 io.c
      436 lex.c
      169 pcmd.c
      78 pfnc.c
      494 plan9.c
      539 simple.c
      74 subr.c
      37 trap.c
      190 tree.c
      420 unix.c
      109 var.c
      85 exec.h
      72 fns.h
        7 getflags.h
      28 io.h
      167 rc.h
      92 syn.y
    5888 total

I would love to see more interpreted languages offer shells with native constructs for operating as daily drivers shells (not just REPLs). When I first started learning Ruby I used `rush`[0] as my main shell. Being immersed in the language, even if there were a few helpers for shell operations, really helped me reason better about Ruby and think in the language. `scsh`[1] was enlightening as well. Ultimately the ergonomics of both pushed me back to more conventional variant but they were really helpful learning mechanisms.

0: https://github.com/adamwiggins/rush 1: https://github.com/scheme/scsh

A few years ago irb got a facelift, so rubish probably represents a more modern take on the shell concept. I tested it and it works too. I wonder how much the everything-is-an-object idea is extended here. Many years ago I learned avisynth + virtualdub and I always liked how they approached filtering. Ffmpeg is great, but I absolutely hate the filter system it uses and the ABSOLUTELY horrible syntax. The ffmpeg devs do not seem to know avisynth, or any alternatives here - so I want object manipulation with a convenient syntax at all times, not just for audio/video data but literally for any data. Naturally ruby would be a good fit by default, but I am unaware of many ruby developers even wanting to go that route. If there are still any ruby developers left that is - ruby has been tanking hard in the last few years, approaching extinction level, just like perl did before.

There has to be a better influx of new users; the old +50 years generation isn't going to keep languages alive really.

Edit: Also I forgot: the idea and implementation is fine, I just think we need much more of that in general. Ruby is kind of in a patchy patchwork situation. Where are the epic projects? Rails is also ancient already.