Temporary Files and Directories in CLIPS

Throughout program execution, we often want to create data that isn’t needed after the program exits. Temporary files and directories are useful for this purpose since they don’t pollute the file system over time.

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;

public class TemporaryFilesAndDirectories {

    private static void check(Exception e) {
        if (e != null) {
            throw new RuntimeException(e);
        }
    }

    public static void main(String[] args) {
        try {
            // The easiest way to create a temporary file is by
            // using Files.createTempFile(). It creates a file and
            // opens it for reading and writing. We provide null
            // as the first argument, so it will create the file
            // in the default temporary-file directory.
            Path tempFile = Files.createTempFile("sample", null);
            System.out.println("Temp file name: " + tempFile);

            // Clean up the file after we're done. The OS is
            // likely to clean up temporary files by itself after
            // some time, but it's good practice to do this
            // explicitly.
            tempFile.toFile().deleteOnExit();

            // We can write some data to the file.
            Files.write(tempFile, new byte[]{1, 2, 3, 4});

            // If we intend to create many temporary files, we may
            // prefer to create a temporary directory.
            // Files.createTempDirectory's arguments are similar to
            // createTempFile's, but it returns a directory Path
            // rather than a file.
            Path tempDir = Files.createTempDirectory("sampledir");
            System.out.println("Temp dir name: " + tempDir);

            tempDir.toFile().deleteOnExit();

            // Now we can synthesize temporary file names by
            // prefixing them with our temporary directory.
            File tempFileInDir = new File(tempDir.toFile(), "file1");
            FileWriter writer = new FileWriter(tempFileInDir);
            writer.write(new char[]{1, 2});
            writer.close();

        } catch (IOException e) {
            check(e);
        }
    }
}

This Java program demonstrates how to work with temporary files and directories. Here’s a breakdown of what it does:

We create a temporary file using Files.createTempFile(). This method creates a new file with a random name in the system’s default temporary-file directory.
We print the name of the temporary file. On Unix-based systems, the directory will likely be /tmp.
We use deleteOnExit() to ensure the file is deleted when the JVM exits. This is similar to using defer in the original example.
We write some data to the file using Files.write().
We create a temporary directory using Files.createTempDirectory().
We print the name of the temporary directory.
We create a new file inside the temporary directory by combining the directory path with a file name.
We write some data to this new file.

Note that Java’s Files class provides methods for creating temporary files and directories, which is more convenient than the lower-level File class. The deleteOnExit() method is used instead of explicit deletion, as Java doesn’t have an equivalent to Go’s defer keyword.

To run this program:

$ javac TemporaryFilesAndDirectories.java
$ java TemporaryFilesAndDirectories
Temp file name: /tmp/sample8979023999133931534.tmp
Temp dir name: /tmp/sampledir4418266304110647149

The exact file and directory names will be different each time you run the program, as they are generated randomly to ensure uniqueness.

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Temporary Files and Directories in CLIPS