How would you read data from a file in Lua? Provide an example that demonstrates the process of reading a text file and printing its contents.

In Lua, reading data from a file involves a few steps: opening the file, reading its contents, and closing the file. Lua provides the "io" library, which contains functions for file input/output operations. To read data from a file, you can use the `io.open()` function to open the file, and then use the `file:read()` function to read its contents.

Here's an example that demonstrates the process of reading a text file and printing its contents:

```
lua`-- Open the file in read mode
local file = io.open("data.txt", "r")

-- Check if the file was successfully opened
if file then
-- Read the file contents
local contents = file:read("a")

-- Close the file
file:close()

-- Print the file contents
print(contents)
else
-- File open error
print("Failed to open the file.")
end`
```
In the example above, we first use the `io.open()` function to open the file named "data.txt" in read mode ("r"). The function returns a file handle, which we assign to the variable `file`.

We then check if the file was successfully opened by verifying that `file` is not `nil`. If the file was opened successfully, we proceed to read its contents using the `file:read("*a")` statement. The `"*a"` argument specifies that we want to read the entire contents of the file.

After reading the file contents into the `contents` variable, we close the file using `file:close()` to release system resources associated with it.

Finally, we print the contents of the file using `print(contents)`.

It's important to handle file open errors or potential issues that may arise while reading a file. In the example, if the file fails to open, an error message is printed, indicating that the file could not be opened.

By following these steps, you can read data from a file in Lua and process its contents according to your specific requirements.