FPGA take testbench Write data to file

integer dout_file;
initial begin
dout_file=$fopen("F:/FPGA/fractional_differential_calculation/test_data_byFPGA_square_512_2.txt"); // Define file location and name
if(dout_file == 0) begin
$display ("can not open the file!"); // If the folder cannot be opened, it displays not open the file!
$stop;
end
end
always @(posedge clk) begin
if(test_data_valid) begin // Write data enable ,
$fdisplay(dout_file,"%d",test_data_D); // Written data
while(!rst_n) $fclose(dout_file);// Close file on reset
end
end