You should be able to call the read
function again.
For example:
read_from_file: process(clk)
variable input_data_column1: natural;
variable input_data_column2: natural;
variable ILine: line;
begin
for i in 0 to NSAMPLES-1 loop
readline (input_vectors, ILine);
read(ILine, input_data_column1);
read(ILine, input_data_column2);
-- Now you can do things like conv_std_logic_vector(input_data_column1, bitwidth) etc
end loop;
end process;
Note: I am not positive if any whitespace will be accepted. Spaces have worked for me.