output filename fix

psrdada_cpp/effelsberg/edd/src/dada_disk_sink_multithread.cpp

@@ -44,7 +44,7 @@ bool DiskSinkMultithread::operator()(RawBytes& block)
     ascii_header_set(_loop_header, "OBS_OFFSET", "%ld", _counter + ii * block.used_bytes() / _nthread);
     ascii_header_set(_loop_header, "FILE_SIZE", "%ld", block.used_bytes() / _nthread);
     std::stringstream fname;
-    fname <<  _start_time << std::setw(20) << std::setfill('0') << _counter + ii * block.used_bytes() / _nthread << ".dada";
+    fname <<  _start_time << std::setw(20) << "_" << std::setfill('0') << _counter + ii * block.used_bytes() / _nthread << ".dada";
     BOOST_LOG_TRIVIAL(debug) << "filename" << fname.str();
     _output_streams[ii].open(fname.str().c_str(), std::ios::out | std::ios::app | std::ios::binary);
     _output_streams[ii].write((char*) _loop_header, HEADER_SIZE);