Userspace

Shell

The shell (/bin/shell.elf, src/usr/shell/) is a line-oriented command interpreter with builtins, pipelines, redirection, scripting, history, and tab completion. The terminal app hosts it as a child process wired through pipes.

Starting Programs

External programs are resolved as /bin/<name>.elf (falling back to /bin/<name>) or run by path. There is no separate exec builtin. See Shell scripting for variables, conditionals, and loops.

Builtins

  • File system: ls, cd, pwd, cat, stat, touch, rm, rmdir, mkdir, cp, mv, tree, find, du, df, mount, write, append, hexdump.
  • Text / pipes: echo, wc, head, tail, grep, sort, uniq, rev, tac, nl, tr.
  • System info: mem, kheap, ps, uptime, date, version, uname, sysinfo, cpuinfo, dmesg, storage.
  • Networking: ping, resolve (ICMP echo is not exposed to userland; ping resolves the target and says so).
  • Audio: sound (kernel parser), play (userspace WAV parser).
  • Scripting / session: run, source, set, unset, alias, unalias, read, test, expr, time, sleep, env, history, which, type, random, true, false, quiet.
  • Process / power: kill, reboot, poweroff, help, clear, exit.

storage shows and sets the storage guard mode (off / read-only / writable). df and mount list volumes with devices, mount points, and flags.

Pipelines and Redirection

  • Pipelines: up to 10 stages joined with |, each junction a real kernel pipe (4 KiB); stages run as forked children with dup2'd ends, waited in order.
  • Pipeable builtins include cat, wc, head, tail, grep, sort, uniq, rev, tac, nl, tr.
  • Redirection: <, >, >> via dup2 with backup descriptors.
  • Exit codes: builtin failure 1, unknown command 127, failed external launch 126, otherwise the child's status. $? exposes the last status and the prompt marker reflects it. 
cat /etc/shell.rc | grep set | wc

Line Editing

  • Movement: left/right, Home/End, Ctrl-A/E.
  • Editing: backspace, Delete, Ctrl-D (delete or exit on empty line), Ctrl-K (kill to end), Ctrl-U (kill line), Ctrl-W (kill word), Ctrl-L (clear).
  • History: up/down with consecutive-duplicate suppression; 32 entries (history).
  • Tab completion: builtin names at the command position; path completion from SYS_GETDENTS elsewhere (unique suffix or common prefix, listing on ambiguity).

Session

  • Prompt: root@unios <cwd> $ (or ! when the last command failed).
  • Initial cwd: /data when present, else /.
  • Startup: sources /etc/shell.rc, falling back to /data/shell.rc.