The data selected in the records control_print, control_print_unknowns, control_print_unknownsrhside or control_print_element will be filtered at output. Thus only a limited amount of data will actually be printed. Here data_item_name is the name of the data item to be filtered, e.g. data_item_name is -node_dof. data_item_index is the index of the data_item_name record which passes the filter. If, by example, data_item_index is 3 then only index 3 passes the filter. If data_item_index is -all then all indices pass the filter. If, by example, data_item_index is -geometry_line 3 (valid if data_item_name is -node or another nodal item) then only records with coordinates located on line 3 pass the filter. If, by example, data_item_index is -geometry_line 3 (valid if data_item_name is -element or another element item) then only element with at least one coordinate located on line 3 pass the filter. If, by example, data_item_index is -ra ...-ra then indices in this range pass the filter. If, by example, data_item_index is -macro 4 and data_item_name is data valid at a node (or element), then only nodes (or elements) generated by the macro number 4 pass the filter (see control_mesh_macro_* for macro's). If, by example, data_item_index is -macro -none and data_item_name is data valid at a node (or element) then only nodes (or elements) not generated by any macro pass the filter (see control_mesh_macro_* for macro's).
By example, if number_0 is 3 then the fourth value of a record passes
the filter. If number_0 is -all the whole
record passes the filter. If, by example, number_0 is
-velx while data_item_name is -node_dof then
only 
-velocities pass the filter.
Some examples are
print_filter 1 -node_dof -all -temp -sigxx (temperatures and xx-stresses)
print_filter 2 -node -geometry_line 3 0 (x-coordinates on line 3)
With control_print_filter you can select if the records control_print, control_print_unknowns or control_print_unknownsrhside (with the same index) should use specific filters (specify the indices of the filter for print_filter_index), should use all filters (specify -all for print_filter_index), or should use no filter at all (specify -none for print_filter_index). Default, if control_print_filter is not specified, all filters will be used for a print option.
Example:
print_filter 1 ...
print_filter 2 ...
...
control_timestep 10 ...
control_print 10 ...
control_print_filter 10 1 (only use filter 1)
...
control_timestep 20 ...
control_print 20 ...
control_print_filter 20 -all (use all filters)
All used filters are placed in-line; thus only data which passes all used filters will be printed.