The following functions are compatible with miscellaneous other standards:
(standardized by POSIX 1.g, which is probably still in draft?)
accept, bind, connect, getdomainname, gethostbyaddr, gethostbyname, getpeername, getprotobyname, getprotobynumber, getservbyname, getservbyport, getsockname, getsockopt, herror, htonl, htons, inet_addr, inet_makeaddr, inet_netof, inet_ntoa, listen, ntohl, ntohs, rcmd, recv, recvfrom, rexec, rresvport, send, sendto, setsockopt, shutdown, socket, socketpair
Of these networking calls, rexec, rcmd and rresvport are implemented in MS IP stack but may not be implemented in other vendors' stacks.
chroot, closelog, cwait, dlclose, dlerror, dlfork, dlopen, dlsym, endgrent, ffs, fstatfs, ftime, get_osfhandle, getdtablesize, getgrent, gethostname, getitimer, getmntent, getpagesize, getpgid, getpwent, gettimeofday, grantpt, initgroups, ioctl, killpg, login, logout, lstat, mknod, memccpy, nice, openlog, pclose, popen, ptsname, putenv, random, readv, realpath, regfree, rexec, select, setegid setenv, seterrno, seteuid, setitimer, setmntent, setmode, setpassent, setpgrp, setpwent, settimeofday, sexecl, sexecle, sexeclp, sexeclpe, sexeclpe, sexecp, sexecv, sexecve, sexecvpe, sigpause, spawnl, spawnle, spawnlp, spawnlpe, spawnv, spawnve, spawnvp, spawnvpe, srandom, statfs, strsignal, strtosigno, swab, syslog, timezone, truncate, ttyslot, unlockpt, unsetenv, usleep, utimes, vfork, vhangup, wait3, wait4, wcscmp, wcslen, wprintf, writev
initgroups does nothing
chroot, mknod, settimeofday, and vhangup always return -1 and sets errno to ENOSYS.
seteuid, setegid, and settimeofday always return 0 and sets errno to ENOSYS.
vfork just calls fork