shell - Interactive kernel command shell

Header: kernel/include/kernel/shell.h
Sources: kernel/arch/i386/shell/shell.c, shell_cmd_*.c, shell_help.c

Provides an interactive read-eval-print loop (REPL) running as a cooperative kernel task (shell_run). Four independent shell instances run concurrently on TTYs 1–4 (Alt+F1–F4 switches focus).

How it works

shell_run loops forever, printing a prompt, reading a line of input, splitting it into tokens, and dispatching to a command handler.

Input (shell_readline)

Handles inline editing: cursor movement, insert-at-point, Backspace, Enter, Ctrl+C (aborts line, prints ^C), history navigation (↑/↓ up to 16 entries), and Tab completion. First token completes against the union of built-in command names and *.elf basenames found in s_app_path. Subsequent tokens complete VFS paths via vfs_complete() - cross-filesystem, so cd /<TAB> enumerates the root (mnt, proc, dev, usr, apps, root, …), cd /mnt/<TAB> lists the live disk mounts (boot, root, cdrom), cat /proc/c<TAB> matches cpuinfo, and ls /apps/<TAB> walks the rootfs apps directory. Globbing (*, ?) on argv is expanded via shell_glob.c before dispatch using the same vfs_complete() enumerator.

Parsing

Splits the input in-place on spaces into up to 8 argv-style tokens. Empty lines are skipped.

Dispatch

Commands are looked up in a module table - a NULL-terminated array of shell_cmd_entry_t[] pointers, one per category file:

static const shell_cmd_entry_t * const cmd_modules[] = {
    man_cmds, help_cmds, display_cmds, system_cmds,
    disk_cmds, fs_cmds, apps_cmds, fileops_cmds, NULL,
};

Each entry is { name, fn, fullscreen }. The fullscreen bit marks handlers that paint directly to the framebuffer (install, exec) - after such a handler returns, shell_dispatch calls shell_restore_screen() which repaints the focused VT’s backing grid plus the status bar. That puts the shell’s history back without waiting for the next keystroke and removes the need for each “fullscreen” command to clean up after itself.

If no built-in matches, the shell tries try_exec_path() on the literal argv[0] (if it’s a path-style /abs or ./rel), then walks the PATH directories appending [.elf]. PATH is the per-task PATH shell variable (settable like any var) and falls back to the built-in default /apps; both command dispatch and first-token tab completion iterate it via shell_path_dir(). Successful ELF execution is also followed by shell_restore_screen() - any ring-3 binary is treated as potentially-fullscreen. vix is no longer a builtin: it resolves through PATH to vix.elf and runs as its own ring-3 task (so it shows up in maktop).

Built-in commands

Filesystem (shell_cmd_fs.c, shell_cmd_fileops.c)

Disk (shell_cmd_disk.c)

System (shell_cmd_system.c)

Application (shell_cmd_apps.c)

Display (shell_cmd_display.c)

Manual (shell_cmd_man.c, shell_help.c)

Functions

shell_run

void shell_run(void);

Enter the interactive shell loop. Never returns. Called as the entry point of each TTY task.

shell_readline

void shell_readline(char *buf, size_t size);

Read one line of input into buf with full inline editing, history, and Tab completion. Used by both the shell REPL and SYS_READ for stdin.