text: """
  Basic subprocess implementation for POSIX which only uses os functions. Only
  implement features required by setup.py to build C extension modules when
  subprocess is unavailable. setup.py is not used on Windows.
  """
  import os
  
  
  # distutils.spawn used by distutils.command.build_ext
  # calls subprocess.Popen().wait()
  class Popen:
      def __init__(self, cmd, env=None):
          self._cmd = cmd
          self._env = env
          self.returncode = None
  
      def wait(self):
          pid = os.fork()
          if pid == 0:
              # Child process
              try:
                  if self._env is not None:
                      os.execve(self._cmd[0], self._cmd, self._env)
                  else:
                      os.execv(self._cmd[0], self._cmd)
              finally:
                  os._exit(1)
          else:
              # Parent process
              pid, status = os.waitpid(pid, 0)
              if os.WIFSIGNALED(status):
                  self.returncode = -os.WTERMSIG(status)
              elif os.WIFEXITED(status):
                  self.returncode = os.WEXITSTATUS(status)
              elif os.WIFSTOPPED(status):
                  self.returncode = -os.WSTOPSIG(status)
              else:
                  raise Exception(f"unknown child process exit status: {status!r}")
  
          return self.returncode
  
  
  def _check_cmd(cmd):
      # Use regex [a-zA-Z0-9./-]+: reject empty string, space, etc.
      safe_chars = []
      for first, last in (("a", "z"), ("A", "Z"), ("0", "9")):
          for ch in range(ord(first), ord(last) + 1):
              safe_chars.append(chr(ch))
      safe_chars.append("./-")
      safe_chars = ''.join(safe_chars)
  
      if isinstance(cmd, (tuple, list)):
          check_strs = cmd
      elif isinstance(cmd, str):
          check_strs = [cmd]
      else:
          return False
  
      for arg in check_strs:
          if not isinstance(arg, str):
              return False
          if not arg:
              # reject empty string
              return False
          for ch in arg:
              if ch not in safe_chars:
                  return False
  
      return True
  
  
  # _aix_support used by distutil.util calls subprocess.check_output()
  def check_output(cmd, **kwargs):
      if kwargs:
          raise NotImplementedError(repr(kwargs))
  
      if not _check_cmd(cmd):
          raise ValueError(f"unsupported command: {cmd!r}")
  
      tmp_filename = "check_output.tmp"
      if not isinstance(cmd, str):
          cmd = " ".join(cmd)
      cmd = f"{cmd} >{tmp_filename}"
  
      try:
          # system() spawns a shell
          status = os.system(cmd)
          if status:
              raise ValueError(f"Command {cmd!r} failed with status {status!r}")
  
          try:
              with open(tmp_filename, "rb") as fp:
                  stdout = fp.read()
          except FileNotFoundError:
              stdout = b''
      finally:
          try:
              os.unlink(tmp_filename)
          except OSError:
              pass
  
      return stdout
  