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+PR_WaitSemaphore
+================
+
+Returns the value of the environment variable.
+
+
+Syntax
+------
+
+.. code::
+
+   #include <pripcsem.h>
+
+   NSPR_API(PRStatus) PR_WaitSemaphore(PRSem *sem);
+
+
+Parameter
+~~~~~~~~~
+
+The function has the following parameter:
+
+``sem``
+   A pointer to a ``PRSem`` structure returned from a call to
+   :ref:`PR_OpenSemaphore`.
+
+
+Returns
+~~~~~~~
+
+:ref:`PRStatus`
+
+
+Description
+-----------
+
+:ref:`PR_WaitSemaphore` tests the value of the semaphore. If the value of
+the semaphore is > 0, the value of the semaphore is decremented and the
+function returns. If the value of the semaphore is 0, the function
+blocks until the value becomes > 0, then the semaphore is decremented
+and the function returns.
+
+The "test and decrement" operation is performed atomically.