Programs

Every executable that ships with BBoeOS lives as a single C file under user/programs/, gets compiled by cc.py, assembled by NASM, and added to the disk image inside bin/. The shell first looks in the root directory, then retries with a bin/ prefix — so cat foo finds bin/cat.

shell.c is the only program loaded directly by the kernel; everything else is launched via SYS_SYS_EXEC (which the shell invokes for any unknown command).

Shell built-ins

These three commands are dispatched inside shell.c itself, not by execing a separate program:

Command	Effect
help	Prints Commands: help reboot shutdown.
reboot	Triple-faults via the 8042 keyboard controller.
shutdown	Tries APM / QEMU / Bochs shutdown hooks. Falls through to APM shutdown failed if none worked. Ctrl-D at the prompt is a shortcut for the same call.

Filesystem

Program	Usage	Source
cat	cat <filename> — print a file to stdout.	user/programs/cat.c
chmod	chmod [+x\|-x] <file> — set or clear the FLAG_EXECUTE bit.	user/programs/chmod.c
cp	cp <src> <dst> — copy a file (preserves mode bits).	user/programs/cp.c
ls	ls [path] — list directory entries; appends / to dirs and * to executables.	user/programs/ls.c
mkdir	mkdir <name> — create a subdirectory under root.	user/programs/mkdir.c
mv	mv <old> <new> — rename a file. Names are capped at 26 chars.	user/programs/mv.c
rm	rm <file> — unlink. Refuses files with FLAG_PROTECTED.	user/programs/rm.c
rmdir	rmdir <dir> — remove an empty subdirectory.	user/programs/rmdir.c

Editors and tools

Program	Usage	Notes
asm	asm <source> <output>	Self-hosted x86 assembler. Resolves %include paths relative to the source’s directory.
draw	draw	40x25 colour canvas with arrow-key cursor; great for sanity-checking the VGA driver and palette.
echo	echo [args...]	Space-separated, newline-terminated.
edit	edit <filename>	Modal text editor with a 448 KB edit buffer + 2.5 KB kill buffer.

Time

Program	Usage	Output
date	date	Wall-clock time as YYYY-MM-DD HH:MM:SS, sourced from the RTC.
uptime	uptime	HH:MM:SS since boot, sourced from the PIT-driven tick counter.

Networking

All four NIC programs require QEMU to be launched with -netdev user,id=net0 -device ne2k_isa,netdev=net0,irq=3,iobase=0x300.

Program	Usage	Notes
arp	arp <ip>	Sends an ARP request and prints the resolved MAC.
dns	dns <domain>	UDP DNS query against the resolver QEMU’s user-net stack hands out (10.0.2.3 by default).
ping	ping <ip\|hostname>	ICMP echo. Resolves names via the same DNS path.

Adding a new program

1. Drop a C file in user/programs/ (see C subset reference for what cc.py accepts).
2. ./make_os.sh — the build script auto-discovers every *.c under user/programs/.
3. Boot, type the program name at the shell. Unknown names fall through to bin/<name>.

The shell’s three built-ins (help, reboot, shutdown) are dispatched inside shell.c’s else if (strcmp(buf, "name") == 0) chain — adding a built-in means a new branch and an updated help string. Adding a regular external command means just a new user/programs/*.c file.