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.
nice allows Cygwin programs to alter their current runtime priority through the use of its incr argument. Cygwin processes can be set to IDLE_PRIORITY_CLASS, NORMAL_PRIORITY_CLASS, HIGH_PRIORITY_CLASS, or REALTIME_PRIORITY_CLASS with the nice call. NORMAL_PRIORITY_CLASS is the default. If you pass a positive number to nice(), then the priority level will decrease by one (within the above list of priorities). A negative number would make it increase by one. It is not possible to change it by more than one at a time without making repeated calls. An increment above REALTIME_PRIORITY_CLASS results in the process staying at that priority. Likewise, a decrement to IDLE_PRIORITY_CLASS has it stay at that priority. Note that in the Win32 API, there are 32 priorities. So currently we only give access to four of these through nice.
seteuid and setegid always return 0 and set errno to ENOSYS.
vfork just calls fork