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+PR_OpenAnonFileMap
+==================
+
+Creates or opens a named semaphore with the specified name
+
+
+Syntax
+------
+
+.. code::
+
+   #include <prshma.h>
+
+   NSPR_API( PRFileMap *)
+   PR_OpenAnonFileMap(
+     const char *dirName,
+     PRSize size,
+     PRFileMapProtect prot
+   );
+
+
+Parameters
+~~~~~~~~~~
+
+The function has the following parameters:
+
+``dirName``
+   A pointer to a directory name that will contain the anonymous file.
+``size``
+   The size of the shared memory.
+``prot``
+   How the shared memory is mapped.
+
+
+Returns
+~~~~~~~
+
+Pointer to :ref:`PRFileMap` or ``NULL`` on error.
+
+
+Description
+-----------
+
+If the shared memory already exists, a handle is returned to that shared
+memory object.
+
+On Unix platforms, :ref:`PR_OpenAnonFileMap` uses ``dirName`` as a
+directory name, without the trailing '/', to contain the anonymous file.
+A filename is generated for the name.
+
+On Windows platforms, ``dirName`` is ignored.