Headless Mode

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Oils has a headless mode with osh --headless, which is meant to divorce the shell and the terminal. You should be able to interact with a shell through a GUI, rather than a terminal.

It uses the "FANOS" protocol we invented, which is ~200 lines of C or ~100 lines of Python. FANOS stands for "file descriptors and netstrings over sockets".

Slogans:

• A shell GUI should have a terminal; it shouldn't be a terminal
• Shell is a language-oriented UI, but that's not the same thing as a terminal-oriented UI

Links

• Blog Posts tagged #headless
  • Interactive Shell Screenshots - the post with a screenshot that I show as a demo. In the web UI, shell input/output is rendered separately from child process input/output
  • Oil's Headless Mode Should Be Useful for UI Research (Notes on the HotOS Unix Shell Panel)
• Docs in the Oils Repo: https://oils.pub/release/latest/doc/headless.html
• #shell-gui on Zulip has many discussions: https://oilshell.zulipchat.com/#narrow/stream/266977-shell-gui
• Shell as an Engine for a GUI or TUI: https://github.com/oilshell/oil/issues/738

Code

• C library (~200 lines): https://github.com/oils-for-unix/oils/blob/master/cpp/fanos_shared.c
• Pure Python 3 library (~100 lines): https://github.com/oils-for-unix/oils/blob/master/client/py_fanos.py
• Go web server, using fanos.go library: https://github.com/subhav/web_shell/

Tips

• Use push-registers { foo } to avoid clobbering $?, BASH_REMATCH, and other registers (VM globals).

TODO

• Demo of how to pass a pipe, and e.g. dump JSON (is our json builtin stable? Or does read --json and read --qtt make more sense?)
• command line option --source (global) (or should it be --use (namespaced) ?)
• Document "registers" ?
• More docs on how to implement a headless client. Join #shell-gui on Zulip for discussion!

Other

This is a non-FANOS interface:

• web_shell prototype: https://github.com/subhav/web_shell/blob/master/command_server.sh
  • descriptor passing would be nice. Uses LD_PRELOAD to trick bash into thinking it's running from a terminal.