Issue #7333: The `posix` module gains an `initgroups()` function providing
access to the initgroups(3) C library call on Unix systems which implement
it.  Patch by Jean-Paul Calderone.
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 0036845..fac37b0 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -136,6 +136,15 @@
    Availability: Unix.
 
 
+.. function:: initgroups(username, gid)
+
+   Call the system initgroups() to initialize the group access list with all of
+   the groups of which the specified username is a member, plus the specified
+   group id. Availability: Unix.
+
+   .. versionadded:: 2.7
+
+
 .. function:: getlogin()
 
    Return the name of the user logged in on the controlling terminal of the