Lua - Appending Files

---

---

Appending file means adding content to the existing contents of a File. Lua provides I/O library to write and manipulate files. We can open a file in append mode using following way−

Simple Model

io.write (content)

Where−

• content− contents to be written or appended to the file as per mode specified while opening file.

Before appending a file, it should be opened using following syntax:

-- Opens a file specified by fileName in append mode
file = io.open(fileName, "a")

-- sets the default input file
io.input(file)

Complete Model

file.write (content)

Where−

• file− file handle returned by io.open().

• content− content to be written/appended to the file.

Before appending a file, it should be opened using following syntax:

-- Opens a file specified by fileName in append mode
file = io.open(fileName, "a")

Append Modes

Let's explore the various options to append content of a file using write() method:

we will use a sample file example.txt as shown below−

example.txt

Welcome to tutorialspoint.com
Simply Easy Learning

Example - Append File Contents

Let us now see how to append a new string to the file.

main.lua

-- append a file content
function appendFile()
   -- Opens a file in append mode, 
   f = io.open("example.txt","a")
   -- write the contents
   f:write("Learning Lua is fun.")
   -- close the file handle
   f:close()
end

-- append the file 
appendFile()

print("Content appended to the file successfully.")

Output

When the above code is built and executed, it produces the following result −

Content written to the file successfully.

File Content

Above code append a string to file example.txt in current directory. You can check the content of example.txt−

Welcome to tutorialspoint.com
Simply Easy Learning
Learning Lua is fun.

Example - Reading and Appending File Contents

Let us now see how to read and append contents to a file.

main.lua

-- append a file content
function appendFile()
   -- Opens a file in append mode,
   f = io.open("example.txt","a+")
   -- set f as default input
   io.input(f)
   -- read content of file
   for line in io.lines() do
      print(line)
   end
   -- set f as default output
   io.output(f)
   -- write the contents
   io.write("Perfection needs practice.")
   -- close the file handle
   f:close()
end

-- write the file
appendFile()

print("Content written to the file successfully.")

Output

When the above code is built and executed, it produces the following result −

Welcome to tutorialspoint.com
Simply Easy Learning
Learning Lua is fun.Perfection needs practice.
Content written to the file successfully.

File Content

Above code create the file example.txt in current directory if not present otherwise overwrite the existing content. You can check the content of example.txt−

Welcome to tutorialspoint.com
Simply Easy Learning
Learning Lua is fun.Perfection needs practice.