Adds the select.PIPE_BUF attribute to expose the system constant.
diff --git a/Doc/library/select.rst b/Doc/library/select.rst
index 351ecfa..469fbac 100644
--- a/Doc/library/select.rst
+++ b/Doc/library/select.rst
@@ -100,6 +100,15 @@
library, and does not handle file descriptors that don't originate from
WinSock.
+.. attribute:: select.PIPE_BUF
+
+ Files reported as ready for writing by :func:`select`, :func:`poll` or
+ similar interfaces in this module are guaranteed to not block on a write
+ of up to :const:`PIPE_BUF` bytes.
+ This value is guaranteed by POSIX to be at least 512.
+
+ .. versionadded:: 2.7
+
.. _epoll-objects: