POSIX compatibility

BBoeOS is POSIX-shaped, not POSIX-compliant. The shell, fd table, syscall numbering, signal handling, errno-style error returns, and a handful of recognisable utilities (cat, ls, rm, echo, pipes, $?, && / ||) will all feel familiar to anyone who has used a Unix. Underneath, large chunks of POSIX are missing on purpose: there is no fork (only exec), only three signals exist, networking is a custom UDP / ICMP datagram syscall (no BSD socket API, no TCP), files have no mtime / uid / gid / mode bits, stat() is a stub, and there is no concept of a working directory or environment.

This document is the honest accounting of what is implemented, what is partly implemented (with notes on what is missing), and what is not implemented at all, so contributors and prospective porters can answer “can I port my program?” in one read.

Two userland code paths exist today:

• cc.py-compiled programs — everything shipped in bin/, plus the libbboeos C library itself. These reach the OS through the shared libbboeos page of FUNCTION_* helpers and the C library surface (<string.h>, <dirent.h>, printf, malloc, …) at user-virt 0x10000, dispatched through the pointer table, and through raw INT 30h syscall wrappers.
• clang-compiled programs linked against user/libbboeos/ — today only the out-of-tree Doom port (ports/doom), which links libbboeos_stubs.o ahead of libbboeos.a so its calls resolve through the same shared libbboeos pointer table. This is the path a larger third-party C program would use.

For deeper detail on individual subsystems, see:

• Syscall interface — full INT 30h reference.
• Programs — usage and source pointers for every shipped utility.
• Architecture — signal delivery, cooperative pipes, paging.
• Memory map — fixed-physical and per-program virtual layout.

Status legend

• ✅ — fully implemented; no POSIX gap that matters for typical use.
• ⚠️ — partial; see the Notes column for what is missing or different.
• ❌ — not implemented.

In the syscall / libc table the “In shipped programs?” column answers a different question: can a cc.py-built program in bin/ reach this today?

• ✅ — yes, via libbboeos FUNCTION_* helper or raw INT 30h wrapper.
• ⚠️ — only via user/libbboeos/, which is not linked into shipped programs yet.
• ❌ — no, regardless of which path; the kernel does not implement it.

Userland utilities

The shipped programs that share a name with a standard POSIX utility. Behaviour notes name only the gap relative to POSIX; see Programs for usage.

Utility	Status	Notes
awk	❌	Not shipped.
basename	❌	Not shipped.
cat	⚠️	Single file or stdin; no -n, -v, -e, -A; no multi-file concat.
chmod	⚠️	+x / -x only — no octal modes, no rwx, no group/other bits (the FS has only FLAG_EXECUTE + FLAG_DIRECTORY).
cmp	❌	Not shipped.
cp	⚠️	Single file to single destination; preserves the execute bit; no -r, -p, -i, no directory destinations.
cut	❌	Not shipped.
date	⚠️	Prints YYYY-MM-DD HH:MM:SS from the RTC. No format string, no -u, no -d.
df	❌	Not shipped.
diff	❌	Not shipped.
dirname	❌	Not shipped.
du	❌	Not shipped.
echo	⚠️	Space-separated, newline-terminated. Supports -n (suppress trailing newline) and -e (interpret \n \t \r \b \e \0 \\ escapes); no \a, \v, \f, \xHH, \NNN, or \c.
env	❌	Not shipped — BBoeOS has no environment variables.
expr	❌	Not shipped.
false	✅	Exits 1.
find	❌	Not shipped.
getopts	❌	Not shipped (would need a shell that exposes argv to scripts; BBoeOS has neither shell scripts nor getopts).
grep	⚠️	Single file or stdin; supports -v (invert), -n (line numbers), -i (case-insensitive). Pattern is a literal substring — no BREs, EREs, anchors, -E, -F, -r, -l, -c, -o; no multi-file.
head	⚠️	Default 10 lines; supports -n N. No -c, no multi-file.
id	❌	Not shipped — BBoeOS has no users.
kill	❌	Not shipped — there is no PID model; only the shell can spawn children via SYS_SYS_PIPELINE2.
ln	❌	Not shipped — the FS has no hard or symbolic links.
ls	⚠️	Output is sorted alphabetically (POSIX default). Appends / to dirs. No * execute marker (POSIX ls adds it only with -F, and stat() is a libc stub). No -l, -a, -R, -1, -t, -F.
mkdir	⚠️	Creates one subdirectory under root only. No -p, no -m.
more	❌	Not shipped.
mv	⚠️	Same-directory rename only — cannot move across directories (the FS is one level deep). No -f, -i.
nl	❌	Not shipped.
od	❌	Not shipped.
paste	❌	Not shipped.
ps	❌	Not shipped — there is no process table exposed to userland; only the shell + up-to-two pipeline children exist.
pwd	❌	Not shipped — there is no working directory; all paths are root-relative.
rm	⚠️	Single file; refuses files with FLAG_PROTECTED. No -r, -f, no globbing.
rmdir	✅	Removes an empty subdirectory.
sed	❌	Not shipped.
sleep	❌	Not shipped as a program. sleep_forever is a test fixture, not POSIX sleep. Use sleep_ms() from user/libbboeos or SYS_RTC_SLEEP directly.
sort	⚠️	Single file or stdin; supports -r (reverse), -n (numeric), -u (unique). In-memory only (60 KB line buffer); no -k, -t, -f, -b, -o, -m; no multi-file.
split	❌	Not shipped.
stty	❌	Not shipped — there is no termios.
tail	⚠️	Single file or stdin (ring-buffer mode); default 10 lines; supports -n N. No -c, no -f (follow), no multi-file.
tee	⚠️	Single output file; no -a (append), no multi-file fan-out.
touch	❌	Not shipped — the FS has no mtime to update; cc.py-built programs can > file to create.
tr	⚠️	Reads stdin only. Two modes: tr <set1> <set2> (translate, expanded sets must be equal length) and tr -d <set1> (delete). Supports a-z-style ranges in both sets; no character classes ([:alpha:]), no backslash escapes, no -s (squeeze), no -c (complement).
true	✅	Exits 0.
tty	❌	Not shipped — there is no /dev/tty abstraction.
umask	❌	Not shipped — there are no mode bits.
uname	❌	Not shipped.
uniq	⚠️	Single file or stdin; supports -c (prefix count) and -d (only duplicated runs). Adjacent-run semantics (does not sort first). No -u, -i, -f, -s.
wc	⚠️	Supports -l, -w, -c. No multi-file summary line, no -m (chars).
who	❌	Not shipped — no users, no utmp.
xargs	❌	Not shipped.

Shell

The shell (user/programs/shell.c) supports line editing (history, Ctrl+R reverse search, Ctrl+K, Ctrl+Y), command chaining with ;, &&, || (bash semantics, equal precedence, left-associative), I/O redirection with <, >, >>, and a single | pipe between exactly two commands. $? expands to the last command’s exit status.

The dispatch chain in dispatch_buffer() recognises three BBoeOS-specific builtins (help, reboot, shutdown — see BBoeOS-specific extras); everything else execs bin/<name>.

Builtin	Status	Notes
.	❌	No shell scripts.
alias / unalias	❌	No aliases.
cd	❌	No per-process working directory.
exit	❌	The shell never exits; Ctrl+D is a shortcut for shutdown.
export / set / unset	❌	No environment, no shell variables (only the parser-level $?).
jobs / fg / bg / wait	❌	No job control, no backgrounding (&).
pwd	❌	No working directory to print.
read	❌	No shell-script read; the line editor is for the interactive prompt only.
times	❌	No per-process time accounting.
trap	❌	No script-level signal handling.
type / command	❌	No name-lookup builtin.
ulimit	❌	No resource limits.

System calls and C library

Each row names a POSIX function, the BBoeOS syscall (or libbboeos helper) that backs it where one exists, and whether a cc.py-built program in bin/ can call it today.

Process control

There is no fork. SYS_SYS_EXEC replaces the current image in place (Linux SysV i386 startup frame: argc / argv / NULL / empty envp). SYS_SYS_PIPELINE2 is shell-only and spawns exactly two cooperatively- scheduled children with cmd1.stdout | cmd2.stdin — see Architecture › Cooperative pipes.

POSIX function	Backing	Status	In shipped programs?	Notes
_exit	SYS_SYS_EXIT (F2h)	✅	✅	Reloads shell; child status returned only via SYS_SYS_PIPELINE2.
atexit	libc	⚠️	⚠️	user/libbboeos only; 8 slots.
execv / execvp / execle / …	—	❌	❌	Wrappers not provided; spell the argv array yourself and call SYS_SYS_EXEC.
execve	SYS_SYS_EXEC (F1h)	⚠️	✅	No envp (always empty); no path search (shell adds the bin/ retry); recursive exec from a child rejected with EINVAL.
exit	libc → _exit	⚠️	⚠️	Only via user/libbboeos; runs up to 8 atexit callbacks then _exit.
fork	—	❌	❌	Not implemented; no plan to add. Only the shell’s SYS_SYS_PIPELINE2 creates additional processes.
getpid / getppid	—	❌	❌	No PID model.
getrlimit / setrlimit	—	❌	❌	No resource limits.
getrusage	—	❌	❌	No per-process accounting.
getuid / geteuid / getgid / getegid	—	❌	❌	No users.
nice / getpriority / setpriority	—	❌	❌	No scheduler priorities; the kernel runs one userland program at a time.
setpgrp / setsid / getpgrp	—	❌	❌	No process groups or sessions.
setuid / setgid	—	❌	❌	No users.
system	libc (stub)	⚠️	⚠️	user/libbboeos stub — always returns -1.
wait / waitpid / waitid	—	❌	❌	SYS_SYS_PIPELINE2 returns child 2’s exit status to the shell, but there is no general wait API.

Signals

Three signals exist: SIGINT (2), SIGPIPE (13), SIGALRM (14). Handlers register via SYS_SYS_SIGNAL; the libbboeos trampoline at handler end calls SYS_SYS_SIGRETURN to restore context. Delivery, dispatch modes, and cooperative interruption of blocking syscalls are documented in Architecture › Signal delivery.

POSIX function	Backing	Status	In shipped programs?	Notes
alarm	SYS_RTC_ALARM (30h)	✅	✅	Second-granularity wrapper around the ms-granularity syscall.
All other POSIX signals (SIGHUP, SIGQUIT, SIGTERM, SIGCHLD, SIGUSR1/2, SIGBUS, SIGSEGV, SIGILL, SIGFPE, …)	—	❌	❌	Faults (#PF, #UD, #DE) EXC0D-trap and exit the program; they are not delivered as signals.
Job-control signals (SIGSTOP / SIGCONT / SIGTSTP / SIGTTIN / SIGTTOU)	—	❌	❌	No job control.
kill / killpg / raise	—	❌	❌	Only the kernel posts signals (SIGINT from Ctrl+C, SIGPIPE from broken pipe writes, SIGALRM from the timer).
Real-time signals	—	❌	❌	No SIGRTMIN..SIGRTMAX, no queueing.
setitimer	SYS_RTC_ALARM (30h)	⚠️	✅	First-fire + interval supported (POSIX ITIMER_REAL shape), but fires only SIGALRM.
sigaction	—	❌	❌	No sa_mask, no SA_RESTART, no siginfo_t.
signal	SYS_SYS_SIGNAL (F6h)	⚠️	✅	Only three signums accepted (SIGINT, SIGPIPE, SIGALRM); bad signum → EINVAL.
sigprocmask / sigpending / sigsuspend	—	❌	❌	No mask / pending / suspend semantics.

File I/O

open flags are O_RDONLY (00h), O_WRONLY (01h), O_CREAT (10h), O_TRUNC (20h); O_RDWR is the bitwise OR of O_RDONLY | O_WRONLY. fstat returns (mode, size) only — no mtime, nlink, uid, gid, or inode number.

POSIX function	Backing	Status	In shipped programs?	Notes
access / faccessat	—	❌	❌	No permission model to query.
close	SYS_IO_CLOSE (10h)	✅	✅	Flushes the dirty bit so fd_close updates the on-disk size.
dup	SYS_IO_DUP (11h)	✅	✅	Singleton devices (e.g. /dev/vga) refuse with an error.
dup2	SYS_IO_DUP2 (12h)	✅	✅	Linux semantics: dup2(N, N) is a no-op; otherwise the target fd is closed first.
fcntl	—	❌	❌	No F_GETFL, F_SETFL, F_GETFD, F_SETFD, F_DUPFD, locks.
fstat	SYS_IO_FSTAT (13h)	⚠️	✅	Returns only (FLAG_*, size); no struct stat in full POSIX shape.
ioctl	SYS_IO_IOCTL (15h)	⚠️	✅	Per-device command dispatch (console, VGA, audio, MIDI); no F_SETFL-style file-flag ioctls.
link / symlink / readlink / unlinkat	—	❌	❌	No links of either kind.
lseek	SYS_IO_SEEK (18h)	⚠️	✅	SEEK_SET / SEEK_CUR / SEEK_END on files; clamped to [0, size]. Pipes / devices are unseekable (no ESPIPE — returns success with no movement).
mkfifo / mknod	—	❌	❌	No named pipes, no device nodes.
open	SYS_IO_OPEN (16h)	⚠️	✅	No O_APPEND, O_EXCL, O_NONBLOCK, O_DIRECTORY, O_CLOEXEC; mode arg ignored.
pipe	—	❌	❌	The kernel implements FD_TYPE_PIPE_R / FD_TYPE_PIPE_W but exposes them only through SYS_SYS_PIPELINE2 (shell-only).
pread / pwrite	—	❌	❌	No atomic offset-aware read/write.
read	SYS_IO_READ (17h)	✅	✅	Works on files, pipes, console, network, devices. On a directory fd, returns ERROR_IS_DIRECTORY (mapped to EISDIR) — use getdents to iterate.
readv / writev	—	❌	❌	No scatter-gather I/O.
select / pselect / poll	—	❌	❌	No multiplexed wait; ioctls return immediately when no data is available.
stat / lstat	libc (stub)	⚠️	⚠️	user/libbboeos stub — always returns -1.
sync / fsync / fdatasync	—	❌	❌	Writes hit the disk on close via the dirty bit.
truncate / ftruncate	—	❌	❌
umask	—	❌	❌	No mode bits.
write	SYS_IO_WRITE (19h)	✅	✅	Same fd-type coverage as read.

Filesystem

bbfs (the built-in floppy FS) and ext2 (read-write, with some limitations) are both single-level under root.

POSIX function	Backing	Status	In shipped programs?	Notes
chdir / fchdir / getcwd	—	❌	❌	No working directory.
chmod	SYS_FS_CHMOD (00h)	⚠️	✅	Sets FLAG_EXECUTE / FLAG_DIRECTORY only. No rwx, no setuid/setgid/sticky.
chown / fchown / lchown	—	❌	❌	No ownership.
chroot / mount / umount	—	❌	❌
getdents	SYS_IO_GETDENTS (14h)	✅	✅	Linux-shaped variable-length records (d_ino, d_reclen, d_type, d_name). See docs/syscalls.md for the record layout.
glob / globfree	—	❌	❌	No shell-side or library-side globbing.
mkdir	SYS_FS_MKDIR (01h)	⚠️	✅	One level under root only; no mode arg; user/libbboeos wrapper is a stub returning -1.
nftw	—	❌	❌	One-level FS; programs walk the root directory directly.
opendir / readdir / closedir / rewinddir	SYS_IO_GETDENTS (14h)	⚠️	❌	Implemented in user/libbboeos/dirent.c for clang-built programs (e.g. the out-of-tree Doom port). No seekdir / telldir; struct dirent exposes d_ino/d_type/d_name only. cc.py-built shipped programs still call SYS_IO_GETDENTS directly.
pathconf / fpathconf	—	❌	❌	MAX_PATH = 64, names ≤26 bytes — fixed at compile time.
realpath	—	❌	❌	No symlinks to resolve and no working directory; all paths are already root-relative.
rename	SYS_FS_RENAME (02h)	⚠️	✅	Same-directory rename only — cannot move across directories. user/libbboeos rename() is a stub.
rmdir	SYS_FS_RMDIR (03h)	✅	✅	Returns ERROR_NOT_EMPTY (mapped to EACCES in libc, not ENOTEMPTY) if the directory is non-empty.
statvfs / fstatvfs	—	❌	❌
unlink / remove	SYS_FS_UNLINK (04h)	⚠️	✅	Files only; cannot unlink a directory; user/libbboeos remove() is a stub.

Memory

POSIX function	Backing	Status	In shipped programs?	Notes
brk	SYS_SYS_BREAK (F0h)	✅	✅	No error path.
malloc / free / calloc / realloc	libc	⚠️	⚠️	user/libbboeos only — real sbrk-backed free-list allocator with coalescing. Shipped cc.py programs roll their own or stay statically sized.
mmap	SYS_VIDEO_MAP (40h)	⚠️	✅	Maps the mode-13h VGA framebuffer (320×200×8bpp) at user-virt 0xB8000000. No file or anonymous mmap.
munmap / mprotect / mlock / madvise	—	❌	❌
sbrk	SYS_SYS_BREAK (F0h)	✅	✅	libc wrapper or do the math inline.
shm_open / shmget / shmat / shmdt	—	❌	❌	No shared memory.

Time

SYS_RTC_DATETIME returns a bare unsigned epoch second; there is no struct timespec. SYS_RTC_SLEEP busy-waits and is interruptible by SIGINT or SIGALRM (returns EINTR).

POSIX function	Backing	Status	In shipped programs?	Notes
clock_gettime / clock_settime / clock_getres	—	❌	❌	No clockid_t, no CLOCK_MONOTONIC proper.
difftime	—	❌	❌
gettimeofday	SYS_RTC_MILLIS (32h)	⚠️	⚠️	user/libbboeos wrapper returns monotonic ms-since-boot, not wall-clock; tz arg ignored.
nanosleep / clock_nanosleep	—	❌	❌	Use sleep_ms() (libc) or SYS_RTC_SLEEP directly.
setitimer / getitimer	SYS_RTC_ALARM (30h)	⚠️	✅	First-fire + interval (ms) supported; only the ITIMER_REAL flavour exists.
strftime / gmtime / localtime / mktime	—	❌	❌	The libbboeos FUNCTION_PRINT_DATETIME prints the canonical YYYY-MM-DD HH:MM:SS form.
time	SYS_RTC_DATETIME (31h)	⚠️	✅	Bare unsigned int — no time_t * argument convention.
times	—	❌	❌	No per-process CPU accounting.
tzset / tzname	—	❌	❌	No timezone database; the RTC is read as-is.

Networking

The networking syscalls are a custom datagram API rather than the BSD socket model: SYS_NET_OPEN returns an fd specialised for IPPROTO_UDP or IPPROTO_ICMP; SYS_NET_SENDTO / SYS_NET_RECVFROM carry destination IP + port in fixed registers. There is no TCP and no socket(AF_INET, …) indirection.

POSIX function	Backing	Status	In shipped programs?	Notes
bind / listen / accept / connect	—	❌	❌	UDP sockets bind implicitly on first sendto.
close	SYS_IO_CLOSE (10h)	✅	✅	Network fds close through the normal io_close path.
getaddrinfo / gethostbyname / getnameinfo	—	❌	❌	Use the standalone dns program.
getsockname / getpeername	—	❌	❌
getsockopt / setsockopt / shutdown	—	❌	❌
if_nametoindex / SIOCGIFADDR / netlink	—	❌	❌	One NIC, fixed name.
recvfrom	SYS_NET_RECVFROM (22h)	⚠️	✅	Non-blocking peek — returns 0 when no datagram is available; kernel-side block-on-wait is a tracked followup.
send / recv / sendmsg / recvmsg	—	❌	❌
sendto	SYS_NET_SENDTO (23h)	⚠️	✅	Custom register convention; UDP carries both ports, ICMP ignores them.
socket	SYS_NET_OPEN (21h)	⚠️	✅	Only SOCK_RAW (proto 0 = ICMP) and SOCK_DGRAM (proto = IPPROTO_UDP or IPPROTO_ICMP); no address-family argument.
TCP (SOCK_STREAM, listen/accept, SYN handshake)	—	❌	❌	UDP / ICMP only.

Terminal / TTY

Input handling is fixed in drivers/console.c (PS/2 + COM1 feeding fd 0, with the line editor in the shell). Programs cannot enter raw mode or control echo / line discipline from userland.

POSIX function	Backing	Status	In shipped programs?	Notes
isatty / ttyname	—	❌	❌
Pseudo-tty (openpty, forkpty, /dev/pts/*)	—	❌	❌
tcgetattr / tcsetattr / cfgetispeed / cfsetispeed / tcdrain / tcflush / tcsendbreak	—	❌	❌	No termios at all.

Standard I/O (stdio)

POSIX function	Backing	Status	In shipped programs?	Notes
feof / ferror / fflush (no-op)	libc	⚠️	⚠️	user/libbboeos only; fflush is a no-op (no buffering to flush).
fgets / getline / getdelim	—	❌	❌	Not in user/libbboeos.
fmemopen / open_memstream	—	❌	❌	No memory-backed FILE *.
fopen / fclose / fread / fwrite / fseek / ftell / fgetc / fputc / fputs / puts / getchar / putchar	libc	⚠️	⚠️	user/libbboeos only. cc.py-built programs use libbboeos FUNCTION_GET_CHARACTER / FUNCTION_PRINT_CHARACTER / FUNCTION_PRINT_STRING / FUNCTION_WRITE_STDOUT directly.
freopen / ungetc / fileno	—	❌	❌	Not in user/libbboeos.
perror / clearerr	—	❌	❌	strerror exists in libc.
popen / pclose	—	❌	❌	No general subprocess API; only the shell’s SYS_SYS_PIPELINE2.
printf / fprintf / vprintf / vfprintf	libc + libbboeos FUNCTION_PRINTF	⚠️	✅	The libbboeos FUNCTION_PRINTF handles the common %s %d %x %c %u set; user/libbboeos vsnprintf is a fuller (314-line) format parser including width / precision / padding.
remove / rename (libc-layer)	libc (stubs)	⚠️	⚠️	user/libbboeos stubs — always return -1.
rewind	libc (no-op)	⚠️	⚠️	user/libbboeos no-op (does not seek).
scanf / fscanf / vscanf / vfscanf	—	❌	❌
setvbuf / setbuf	—	❌	❌	No buffered-IO modes.
sprintf / snprintf / vsprintf / vsnprintf	libc	⚠️	⚠️	user/libbboeos only.
sscanf	libc (stub)	⚠️	⚠️	user/libbboeos stub — always returns 0.
tmpfile / mkstemp / mkdtemp	—	❌	❌

String, ctype, stdlib

All of the rows below are implemented in user/libbboeos/ (string.c, ctype.c, stdlib.c). Reachability from cc.py-built shipped programs is tracked per-row in the “In shipped programs?” column — the <string.h> surface dispatches through the libbboeos pointer table, while the rest are available only to clang programs that statically link libbboeos.a.

POSIX function	Backing	Status	In shipped programs?	Notes
abs / labs	libc	⚠️	⚠️	abs only; no labs / llabs.
atof	libc (stub)	⚠️	⚠️	user/libbboeos stub — always returns 0.0.
atoi / atol	libc	⚠️	⚠️	user/libbboeos only.
div / ldiv / lldiv	—	❌	❌
Full ctype.h (isalnum / isalpha / iscntrl / isdigit / isspace / islower / isupper / isprint / ispunct / isxdigit / tolower / toupper)	libc	⚠️	⚠️	user/libbboeos only.
getenv	libc (stub)	⚠️	⚠️	user/libbboeos stub — always returns NULL. No environment.
locale (setlocale, LC_*, collation, wide chars)	—	❌	❌	ASCII only.
memcpy / memmove / memset / memcmp / memchr	libc	⚠️	⚠️	user/libbboeos only.
posix_memalign / aligned_alloc	—	❌	❌	No alignment-aware allocator.
qsort / bsearch	libc	⚠️	⚠️	user/libbboeos only (Sedgewick quicksort, recursive binary search).
rand / srand	libc	⚠️	⚠️	LCG PRNG.
setenv / unsetenv / putenv	—	❌	❌	No environment.
strcpy / strncpy / strcat / strncat / strcmp / strncmp / strcasecmp / strncasecmp / strchr / strrchr / strstr / strlen / strdup / strerror	libc	⚠️	⚠️	user/libbboeos only.
strerror_r / strsignal	—	❌	❌	Not in user/libbboeos.
strspn / strcspn / strpbrk	—	❌	❌	Not in user/libbboeos.
strtod / strtof	—	❌	❌	No floating-point string conversion (matches the atof stub).
strtok / strtok_r	—	❌	❌	Not in user/libbboeos.
strtol / strtoul	libc	⚠️	⚠️	user/libbboeos only.
strtoll / strtoull	—	❌	❌	No 64-bit string conversion.
system	libc (stub)	⚠️	⚠️	user/libbboeos stub — always returns -1.

Math

POSIX function	Backing	Status	In shipped programs?	Notes
asin / acos / atan / sinh / cosh / tanh / expm1 / log1p / cbrt / hypot / fmod / modf / frexp / ldexp / round / trunc	—	❌	❌	Not in user/libbboeos/math.c.
sin / cos / tan / atan2 / sqrt / exp / log / log2 / log10 / pow / floor / ceil / fabs (+ f variants)	libc	⚠️	⚠️	user/libbboeos/math.c — all implemented via x87 inline asm. Float variants wrap the double form.

Process IPC

POSIX function	Backing	Status	In shipped programs?	Notes
Anonymous pipes (kernel side)	FD_TYPE_PIPE_R / FD_TYPE_PIPE_W	⚠️	⚠️	Implemented; exposed only via SYS_SYS_PIPELINE2 (shell creates the pipe pair on behalf of cmd1 | cmd2).
Named pipes (mkfifo)	—	❌	❌
pipe (user-callable)	—	❌	❌
POSIX message queues (mq_*)	—	❌	❌
SysV message queues (msgget / msgsnd / msgrcv)	—	❌	❌
SysV semaphores (semget / semop / semctl)	—	❌	❌
SysV / POSIX shared memory	—	❌	❌

Threading

Single-threaded only. Within a “program” there is no concurrency primitive beyond signal handlers (which run on the same stack via the libbboeos trampoline).

POSIX function	Backing	Status	In shipped programs?	Notes
Atomics / stdatomic.h	—	❌	❌
Mutexes / condition variables / barriers / rwlocks	—	❌	❌
POSIX semaphores (sem_init / sem_wait / sem_post / sem_destroy)	—	❌	❌
pthread_create / pthread_join / pthread_detach / pthread_* (all of it)	—	❌	❌

Setjmp, errno, misc

user/libbboeos maps a subset of ERROR_* to errno: ENOSPC, EEXIST, EFAULT, EINTR, EINVAL, EACCES (catch-all for ERROR_NOT_EMPTY / ERROR_NOT_EXECUTE / ERROR_PROTECTED), ENOENT, with EIO as the default fallback. POSIX-distinct codes like EBADF, EISDIR, ENOTDIR, ESPIPE, ENOTEMPTY, EPERM are not synthesised separately.

POSIX function	Backing	Status	In shipped programs?	Notes
abort	libc	⚠️	⚠️	user/libbboeos only — exits 134.
assert	libc	⚠️	⚠️	user/libbboeos/assert.h — fprintf(stderr, …) + abort().
dlopen / dlsym / dlclose	—	❌	❌	All code is statically compiled in.
errno	libc	⚠️	⚠️	user/libbboeos only — see code list above.
getopt	user/libbboeos/include/getopt.h	⚠️	✅	Header-only short-option parser used by echo, grep, head, sort, tail, tr, uniq, wc. No combined flags (-lw), no value-attached form (-nN), no -- sentinel, no argv permutation.
regex (regcomp / regexec)	—	❌	❌
setjmp / longjmp	libc (asm)	⚠️	⚠️	user/libbboeos/setjmp.S — 6-slot jmp_buf (esp/ebp/eip + 3 callee-saved).
sigsetjmp / siglongjmp	—	❌	❌	No signal mask to save.
sysconf / confstr	—	❌	❌	No runtime configuration query API; limits are compile-time.

Filesystem metadata

Field	bbfs	ext2	Notes
Execute bit	✅	✅	The only “permission” bit — FLAG_EXECUTE.
Extended attributes / ACLs	❌	❌
File name (≤26 bytes)	✅	✅	Both filesystems store names in 27-byte slots.
File size (32-bit)	✅	✅
File type (regular vs directory)	✅	✅	Tracked via FLAG_DIRECTORY.
Hard links	❌	❌
Inode number	❌	✅	The ext2 driver tracks inodes; bbfs has no inode concept.
Link count (nlink)	❌	❌
Max path	❌	❌	Hard cap MAX_PATH = 64; only one / allowed (single-level subdirs under root).
Mode bits (rwx ×3)	❌	❌
mtime / atime / ctime	❌	❌
Owner uid / gid	❌	❌
Sparse files	❌	❌
Special files (block / char / FIFO / socket)	❌	❌
Symbolic links	❌	❌

BBoeOS-specific extras

These have no POSIX counterpart but are part of the OS surface area. Documented here so a porter knows they exist (and is not surprised by unfamiliar names in the source).

• Programs: asm (self-hosted assembler), edit (modal text editor), draw (40×25 VGA canvas), arp / dns / ping (network diagnostics), seq (GNU-style counter), yes (traditional BSD repeater), pipe_producer / pipe_consumer / pipe_drain / pipe_spam (pipeline test fixtures), recursive_exec_test, fd_helpers, exit_status, sleep_forever, uptime.
• Shell builtins: help (lists the BBoeOS-specific builtins), reboot (triple-faults via the 8042 keyboard controller), shutdown (tries APM / QEMU / Bochs hooks).
• Syscalls: SYS_VIDEO_MAP, SYS_NET_MAC, SYS_RTC_MILLIS, SYS_RTC_UPTIME, SYS_SYS_REBOOT, SYS_SYS_SHUTDOWN, SYS_SYS_PIPELINE2.
• libbboeos helpers: FUNCTION_PRINT_IP, FUNCTION_PRINT_MAC, FUNCTION_PRINT_DATETIME, FUNCTION_PRINT_BYTE_DECIMAL, FUNCTION_PRINT_DECIMAL, FUNCTION_PRINT_HEX.
• Device fds: /dev/vga (mode-13h framebuffer + palette ioctls), /dev/audio (SB16 PCM stream), /dev/midi (OPL3 register-write stream).
• user/libbboeos extensions (non-POSIX): alarm_ms(), sleep_ms(), uptime_ms(), video_map().

Updating this document

When adding a new SYS_* syscall, a shell builtin, or a POSIX-named program, update the relevant table in docs/posix.md in the same commit (this mirrors the existing docs/CHANGELOG.md + docs/syscalls.md discipline). Run python3 tools/wrap_md.py docs/posix.md after editing.