Create directory if needed for GnuplotWriter and GnuplotWriter1D

src/output/GnuplotWriter.cpp

@@ -294,6 +294,8 @@ GnuplotWriter::_write(const MeshType& mesh,
       item_data_variant);
   }
 
+  createDirectoryIfNeeded(m_base_filename);
+
   for (size_t i_rank = 0; i_rank < parallel::size(); ++i_rank) {
     if (i_rank == parallel::rank()) {
       std::ofstream fout(_getFilename(), std::ios_base::app);

src/output/GnuplotWriter1D.cpp

@@ -323,6 +323,8 @@ GnuplotWriter1D::_write(const MeshType& mesh,
 
   std::ofstream fout;
 
+  createDirectoryIfNeeded(m_base_filename);
+
   if (parallel::rank() == 0) {
     fout.open(_getFilename());
     if (not fout) {