File::Constants provides file-related constants. All possible file constants are listed in the documentation but they may not all be present on your platform.
If the underlying platform doesn’t define a constant the corresponding Ruby constant is not defined.
Your platform documentations (e.g. man open(2)) may describe more detailed information.
Constants
NULL = rb_fstring_cstr(null_device)
LOCK_NB = INT2FIX(LOCK_NB)
LOCK_UN = INT2FIX(LOCK_UN)
LOCK_EX = INT2FIX(LOCK_EX)
LOCK_SH = INT2FIX(LOCK_SH)
TMPFILE = INT2FIX(O_TMPFILE)
DIRECT = INT2FIX(O_DIRECT)
NOATIME = INT2FIX(O_NOATIME)
NOFOLLOW = INT2FIX(O_NOFOLLOW)
RSYNC = INT2FIX(O_RSYNC)
DSYNC = INT2FIX(O_DSYNC)
SYNC = INT2FIX(O_SYNC)
SHARE_DELETE = INT2FIX(O_SHARE_DELETE)
BINARY = INT2FIX(O_BINARY)
NOCTTY = INT2FIX(O_NOCTTY)
TRUNC = INT2FIX(O_TRUNC)
NONBLOCK = INT2FIX(O_NONBLOCK)
EXCL = INT2FIX(O_EXCL)
CREAT = INT2FIX(O_CREAT)
APPEND = INT2FIX(O_APPEND)
RDWR = INT2FIX(O_RDWR)
WRONLY = INT2FIX(O_WRONLY)
RDONLY = INT2FIX(O_RDONLY)