Lua - Closing Files

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Lua provides I/O library to read and manipulate files. Now once file processing is complete, it is a good practice to call close() method. Although Lua does memory management automatically and close the resources.

Simple Model

io.close (file)

Where−

• file− file handle .

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

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

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

Complete Model

file:close ()

Where−

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

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

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

But if we're opening multiple files and garbage collector is not running at that time then we may face following problems. −

• Opened files may reach to maximum level until garbage collector closes them automatically.

• Some platform may not allow to write to file if it is already opened and not closed.

• Data may not be stored to a file by write() operation if close is not called.

• Memory overflow can occur.

Example - Closing File in Simple Model

Let us now see how to close a file in simple model first.

main.lua

-- read a file content and returns the same
function readFile()
   -- Opens a file in read
   f = io.open("example.txt","r")
   -- set the file as default input
   io.input(f)
   -- read first line
   print(io.read())
   -- read next line   
   print(io.read())
   -- close the file
   io.close()
   -- return the contents
   return contents
end

-- read the file
readFile()

Output

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

Welcome to tutorialspoint.com
Simply Easy Learning

Example - Closing File in Complete Model

Let us now see how to close a file in complete model first.

main.lua

-- read a file content and returns the same
function readFile()
   -- Opens a file in read
   f = io.open("example.txt","r")
   -- read first line
   print(f:read())
   -- read next line   
   print(f:read())
   -- close the file
   f:close()
   -- return the contents
   return contents
end

-- read the file
readFile()

Output

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

Welcome to tutorialspoint.com
Simply Easy Learning