d_type-check

#!/usr/bin/python
# Exit 0 if "." has useful d_type information, else 1.
# Intended to exit 0 only on Linux/GNU systems.
import sys

fail = 1
try:
  import ctypes

  (DT_UNKNOWN, DT_DIR,) = (0, 4,)

  class dirent(ctypes.Structure):
    _fields_ = [
      ("d_ino", ctypes.c_long),
      ("d_off", ctypes.c_long),
      ("d_reclen", ctypes.c_ushort),
      ("d_type", ctypes.c_ubyte),
      ("d_name", ctypes.c_char*256)]

  direntp = ctypes.POINTER(dirent)

  # FIXME: find a way to avoid hard-coding libc's so-name.
  libc = ctypes.cdll.LoadLibrary("libc.so.6")
  libc.readdir.restype = direntp

  dirp = libc.opendir(".")
  if dirp:
    ep = libc.readdir(dirp)
    if ep:
      name = ep.contents.d_name
      if (name == "." or name == "..") and ep.contents.d_type == DT_DIR:
        fail = 0

except:
  pass

sys.exit(fail)