# Method Stdio.Fd()->is_open()

Method is_open

  ``int` is_open()`

Description

  Returns true if the file is open.

Note

  If the file is a socket that has been closed from the remote side, this function might still return true.

Note

  Most methods can't be called for a file descriptor that isn't open. Notable exceptions errno, mode, and the set and query functions for callbacks and backend.