How to read content from text file and How to write content in text file in VHDL

--PROGRAM TO READ CONTENT FROM ONE FILE AND WRITE IT IN to ANOTHER FILE

--THIS PROGRAM HAS TO BE WRITTEN IN TESTBENCH MODULE

--INPUT AND OUTPUT text FILES SHOULD BE PRESENT IN YOUR PROJECT FOLDER

library ieee;

use ieee.std_logic_1164.all;

use STD.Textio.all;--PACKAGE CONTAIN FUNTIONS RELATED TO FILE READ/WRITE OPERATION

entity FA_TESTS is

end FA_TESTS;

architecture behavioral of FA_TESTS is

begin

process

file infile :text; --DEFINES INPUT FILE_HANDLE AND TYPE OF FILE

file outfile :text;--DEFINES INPUT FILE_HANDLE AND TYPE OF FILE

variable buff: line;--VARIABLE WITH TYPE LINE TO READ COMPLETE LINE/ROW AT A TIME

begin

file_open(infile,"gnc.txt",read_mode);--OPEN FILE NAME "GNC.TXT' TO READ CONTENT FROM THAT FILE

file_open(outfile,"gncc.txt", write_mode);--OPEN FILE NAME "GNCC.TXT" TO WRITE CONTENT TO THAT FILE

for i in 1 to 4 loop  --AS INPUT FILE "GNC.TXT" CONTAIN CONTENT OF 4 LINE

readline(infile, buff); --TO READ A LINE FROM INPUT FILE

writeline(outfile,buff);--TO WRITE A LINE TO OUTPUT FILE

end loop;

file_close(infile);--NECESSARY TO CLOSE OPEN FILE

file_close(outfile); --NECESSARY TO CLOSE OPEN FILE

wait;--TO HALT THE PROGRAM / TO AVOID INFINITE EXECUTION OF PROGRAM

end process;

end  behavioral;