Chapter 25 helper add

Author: Artiom N.

src/book01/ch25/python/cloexec_helper.py

@@ -0,0 +1,13 @@
+#!/usr/bin/env python3
+
+import fcntl
+
+
+def set_close_exec(fd):
+    """
+    Helper to set CLOEXEC.
+
+    :fd: int file descriptor
+    """
+    flags = fcntl.fcntl(fd, fcntl.F_GETFD)
+    fcntl.fcntl(fd, fcntl.F_SETFD, flags | fcntl.FD_CLOEXEC)