Shulou(Shulou.com)06/03 Report--

This article mainly explains "how to use Lua to manipulate the data in the file". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to manipulate the data in the file with Lua".

Install Lua

If you are using Linux, you can install Lua from your distribution library. On macOS, you can install Lua from MacPorts or Homebrew. On Windows, you can install Lua from Chocolatey.

After installing Lua, open your favorite text editor and get ready to start.

Use Lua to read files

Lua uses the io library for data input and output. The following example creates a function called ingest to read data from a file and then parses it with the: read function. When you open a file in Lua, there are several modes that can be enabled. Because I only need to read data from this file, I use the r (for "read") mode:

Function ingest (file) local f = io.open (file, "r") local lines = f:read ("* all") f:close () return (lines) end myfile=ingest ("example.txt") print (myfile)

In this code, you notice that the variable myfile is created to trigger the ingest function, so it receives anything returned by that function. The ingest function returns the number of lines in the file (0 from a variable called lines. When the contents of the myfile variable are printed in the last step, the number of lines in the file appears in the terminal.

If the file example.txt contains configuration options, I'll write some extra code to parse the data, possibly using another Lua library, depending on whether the configuration is stored in an INI file, YAML file, or other format. If the data were SVG graphics, I would write extra code to parse XML, possibly using Lua's SVG library. In other words, once the data read by your code is loaded into memory, it can be manipulated, but they all need to load the io library.

Write data to a file with Lua

Whether you want to store data that users create with your application, or just metadata about what users do in the app (for example, game saves or recently played songs), there are many good reasons to store data for future use. In Lua, this is done through the io library, open a file, write data to it, and then close the file:

Function exgest (file) local f = io.open (file, "a") io.output (f) io.write ("hello world\ n") io.close (f) end exgest ("example.txt")

To read the data from the file, I opened the file in r mode, but this time I used a (for "append") to write the data to the end of the file. Because I write plain text to the file, I add my own newline character (/ n). Usually, instead of writing the original text to a file, you may use an additional library instead of writing to a specific format. For example, you might use INI or YAML libraries to help write configuration files, XML libraries to write XML, and so on.

File mode

When you open a file in Lua, there are some safeguards and parameters that define how to handle the file. The default value is r, which allows you to read-only data:

R read only

W if the file does not exist, overwrite or create a new file.

R + read and overwrite.

An append data to the file, or create a new file if the file does not exist.

A + read the data, append the data to the file, or create a new file if the file does not exist.

There are others (for example, b stands for binary format), but these are the most common. For complete documentation, please refer to the excellent Lua documentation on Lua.org/manual.

Lua and Files

Like other programming languages, Lua has a large number of libraries that support access to the file system to read and write data. Because Lua has a consistent and simple syntax, it is easy to do complex processing of file data in any format. Try using Lua in your next software project, or as an API for a C or C++ project.

Thank you for your reading, the above is the content of "how to use Lua to manipulate the data in the file". After the study of this article, I believe you have a deeper understanding of how to use Lua to manipulate the data in the file. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.