New lines in writing to files

Hello! I need help. What I want to do is open a file and write a variable to it in a new line of the program.
For ex:
File before I write to it:

Hello

File after I write to it:

Hello
World

Any help?

Do you mean the append mode?

--# Creating the file and clearing it if it exists
local file = fs.open("<file>", "w")
file.write("Hello")
file.close()

--# Opening and adding the new data without clearing the file
local file = fs.open("<file>","a")
file.writeLine("World") -- writes to a newline
file.close()

Check out the wiki about fs.open for more information