/*D
   MPI_Attr_get - Retrieves attribute value by key

Synopsis:
.vb
int MPI_Attr_get(MPI_Comm comm, int keyval, void *attribute_val, int *flag)
.ve

Input Parameters:
+ comm - communicator to which attribute is attached (handle)
- keyval - key value (integer)

Output Parameters:
+ attribute_val - attribute value, unless flag = false (None)
- flag - true if an attribute value was extracted; false if no attribute is associated with the key (logical)

.N Deprecated
   The replacement for this routine is 'MPI_Comm_get_attr'.

.N ThreadSafe

.N Errors
.N MPI_SUCCESS
.N MPI_ERR_OTHER

.seealso: MPI_Attr_put, MPI_Keyval_create, MPI_Attr_delete, MPI_Comm_get_attr
D*/

