The shell

s – speaks Bash, so your scripts just keep running. And Tab knows every command.

s                  interactive
s skript.sh ARG …  run a script
s -c 'befehl'      one command
s -e -x -u -o pipefail   like in bash

Bash scripts run

Almost everything you know from Bash is there: variables, pipes, if/for/while/case, functions, [[ … ]] with patterns and =~, arrays and associative arrays, $(( )), here documents, <(befehl), all ${x…} expansions, set -euo pipefail, select, name references (declare -n), extglob and **/.

The proof of the pudding: Homebrew's brew and git filter-branch run under s with the same output as under bash. Every case is tested against bash 5.

Typing is fun

Tab completes commands (with long and old names and description), options (with explanation), paths, variables – and knows from the spec whether an argument is a path, folder, process or user. Tab twice shows the list.
History with the arrow keys, Ctrl+R searches it, !! and !$ work too. Saved in ~/.s_history.
The usual keys: Ctrl+A/E/K/U/W/Y, Alt+B/F, Alt+. fetches the last word.
Typo? s suggests the closest name: “did you mean …?”
Old names: cp, mv, ls … automatically become c, m, l.

Startup file: ~/.src. Messages come in German, on one line. The prompt is benutzer@rechner:ordner $ when you're logged in (e.g. over SSH), otherwise just ordner $ – your own prompt via PS1 like in bash.

What's (still) missing

Job control (fg, bg, Ctrl+Z), coproc, read -t, ulimit, times, caller, wait -n. complete is accepted but has no effect – s uses the specs after all.

Where it runs

On NULLos itself! If /bin/s exists, the kernel starts the shell right at boot. Pipes, loops, $( ) and functions work there. exit takes you back to the small kernel shell. On the Mac: all tests green.

For small devices without fork there is a version that starts programs through a single system call.