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‎.gitignore‎

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@@ -4,3 +4,5 @@ pom.xml.releaseBackup
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pom.xml.versionsBackup
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pom.xml.next
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release.properties
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*.iml
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.idea/

‎README.md‎

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# java-file-change-watcher
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The JavaFileChangeWatcher is a small programm (Jar File: ~10Kb) which watches a single file for changes and executes
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a command if the file was created or changed.
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The program aims to be similar to [inotifywatch](https://github.com/rvoicilas/inotify-tools) but platform independent
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so that it works on Windows as well.
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# Features
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- ...uses the Watcher-API introduced in Java 7 which should make it get along with low system resources.
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- ...after a file change was detected waits another second before executing. If another change is detected during that
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second start to wait another second to reduce command executions if many alterations happen to a file in a small time.
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# Usage
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java -jar filewatch.jar [-v] <fileToWatch> <commandToExecute>
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Remember that "commandToExecute" is not executed in a shell, so you cannot do any fancy stuff like string expansion (*).
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I suggest creating a script file (.bat on Windows, .sh on Linux) with your fancy things and just let this program call
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that script.
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# Alternatives
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The following alternatives I encountered:
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- [Using the PowerShell on Windows](http://blogs.technet.com/b/heyscriptingguy/archive/2004/10/11/how-can-i-automatically-run-a-script-any-time-a-file-is-added-to-a-folder.aspx) (I could not get that one to work, but I never worked with the MS Powershell before so it's probably just me)
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- [Belvedere](http://ca.lifehacker.com/341950/belvedere-automates-your-self+cleaning-pc) (Is Windows only and I wanted something that works on Linux as well for testing. Additionally it is not lightweight)
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- [when_changed](https://github.com/benblamey/when_changed) (Similar to this one, but written in C#. Maybe it works with Mono on Linux, I did not test)
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If you know another tool which you think may be helpful for others to find, feel free to create a pull request.
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# Contributing
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Feel free to create a pull request if you think something important is missing. Please submit tests with your code and
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remember that this tool is meant to be lightweight, so no huge add ons.

‎pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>de.softwertiger.filewatch</groupId>
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<artifactId>filewatch</artifactId>
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<version>1.0</version>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<version>3.1</version>
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<configuration>
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<source>1.8</source>
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<target>1.8</target>
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</configuration>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-jar-plugin</artifactId>
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<configuration>
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<archive>
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<manifest>
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<addClasspath>true</addClasspath>
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<mainClass>de.softwertiger.filewatch.cli.Main</mainClass>
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</manifest>
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</archive>
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</configuration>
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</plugin>
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</plugins>
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</build>
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<dependencies>
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<dependency>
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<groupId>org.testng</groupId>
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<artifactId>testng</artifactId>
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<version>6.8.8</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.mockito</groupId>
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<artifactId>mockito-all</artifactId>
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<version>1.9.5</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎src/main/java/de/softwertiger/filewatch/DelayCallMerger.java‎

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package de.softwertiger.filewatch;
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import java.util.concurrent.atomic.AtomicInteger;
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public class DelayCallMerger implements Runnable {
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private final Runnable delegate;
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private volatile AtomicInteger runCounter = new AtomicInteger(0);
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public DelayCallMerger(final Runnable delegate) {
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this.delegate = delegate;
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}
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@Override
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public void run() {
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int id = runCounter.incrementAndGet();
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new Thread() {
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@Override
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public void run() {
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try {
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Thread.sleep(1000);
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} catch (InterruptedException e) {
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e.printStackTrace();
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return;
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}
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synchronized (DelayCallMerger.this) {
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if (id == runCounter.get()) {
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delegate.run();
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}
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}
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}
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}.start();
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}
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}

‎src/main/java/de/softwertiger/filewatch/OnFileChangeRunner.java‎

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package de.softwertiger.filewatch;
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import java.io.IOException;
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import java.nio.file.FileSystems;
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import java.nio.file.Path;
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import java.nio.file.WatchEvent;
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import java.nio.file.WatchKey;
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import java.nio.file.WatchService;
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import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;
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import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;
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public class OnFileChangeRunner {
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private final Path watchDir;
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private final Path watchFile;
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private final WatchService watchService;
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private OnFileChangeRunner(final Path watchFile) throws IOException {
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this.watchFile = watchFile;
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watchDir = watchFile.getParent();
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watchService = FileSystems.getDefault().newWatchService();
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watchDir.register(watchService, ENTRY_CREATE, ENTRY_MODIFY);
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}
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public static OnFileChangeRunner registerForFile(final Path watchFile) throws IOException {
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return new OnFileChangeRunner(watchFile);
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}
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public void runOnFileChange(final Runnable runnable) {
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try {
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tryRunOnFileChange(runnable);
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} catch (IOException e) {
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throw new Error(e);
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}
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}
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private void tryRunOnFileChange(final Runnable runnable) throws IOException {
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try {
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final WatchKey take = watchService.take();
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while (!Thread.interrupted()) {
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for (final WatchEvent<?> watchEvent : take.pollEvents()) {
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final WatchEvent<Path> ev = cast(watchEvent);
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if (watchFile.equals(watchDir.resolve(ev.context()))) {
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runnable.run();
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}
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}
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}
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} catch (InterruptedException e) {
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// Ignore
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}
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}
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@SuppressWarnings("unchecked")
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private static <T> WatchEvent<T> cast(WatchEvent<?> event) {
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return (WatchEvent<T>) event;
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}
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}

‎src/main/java/de/softwertiger/filewatch/StreamUtil.java‎

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package de.softwertiger.filewatch;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.PrintStream;
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import java.util.concurrent.ThreadFactory;
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import java.util.concurrent.atomic.AtomicInteger;
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public class StreamUtil {
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private final ThreadFactory threadFactory;
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private final int bufferSize;
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public StreamUtil() {
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this(new ThreadFactory() {
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private final AtomicInteger threadNumber = new AtomicInteger(1);
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@Override
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public Thread newThread(final Runnable r) {
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return new Thread(r, "stream-util-" + threadNumber);
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}
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}, 8192);
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}
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StreamUtil(final ThreadFactory threadFactory, final int bufferSize) {
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this.threadFactory = threadFactory;
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this.bufferSize = bufferSize;
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}
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public Thread forwardStream(final InputStream in, final PrintStream out) {
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Thread thread = threadFactory.newThread(() -> {
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byte[] buffer = new byte[bufferSize];
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int read;
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try {
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while((read = in.read(buffer)) > -1) {
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out.write(buffer, 0, read);
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}
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} catch (IOException e) {
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e.printStackTrace();
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}
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});
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thread.start();
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return thread;
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}
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}

‎src/main/java/de/softwertiger/filewatch/cli/IllegalCommandLineOptionsException.java‎

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package de.softwertiger.filewatch.cli;
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public class IllegalCommandLineOptionsException extends RuntimeException {
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}

‎src/main/java/de/softwertiger/filewatch/cli/Main.java‎

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package de.softwertiger.filewatch.cli;
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import de.softwertiger.filewatch.DelayCallMerger;
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import de.softwertiger.filewatch.OnFileChangeRunner;
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import de.softwertiger.filewatch.StreamUtil;
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import java.io.IOException;
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public class Main {
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private static final StreamUtil streamUtil = new StreamUtil();
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private final Options options;
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public Main(final Options options) throws IOException {
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this.options = options;
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if (options.isVerbose()) {
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System.out.println("Watching <" + options.getFileToWatch() + "> for changes");
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}
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OnFileChangeRunner
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.registerForFile(options.getFileToWatch())
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.runOnFileChange(new DelayCallMerger(this::tryRunCommand));
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}
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public static void main(String[] args) throws Exception {
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try {
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new Main(Options.parseCommandLineOptions(args));
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} catch (IllegalCommandLineOptionsException e) {
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System.out.println("Usage: fileWatcher [-v] <fileToWatch> <commandToExecute>");
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}
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}
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private void tryRunCommand() {
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if (options.isVerbose()) {
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System.out.println("File has changed. Executing...");
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}
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try {
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final Process process = Runtime.getRuntime().exec(options.getCommand());
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streamUtil.forwardStream(process.getInputStream(), System.out);
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streamUtil.forwardStream(process.getErrorStream(), System.err);
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} catch (IOException e) {
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throw new Error(e);
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}
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}
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}

‎src/main/java/de/softwertiger/filewatch/cli/Options.java‎

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package de.softwertiger.filewatch.cli;
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import java.nio.file.Path;
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import java.nio.file.Paths;
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public class Options {
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private final boolean verbose;
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private final Path fileToWatch;
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private final String command;
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private Options(final boolean verbose, final Path fileToWatch, final String command) {
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if (fileToWatch == null || command == null) {
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throw new IllegalCommandLineOptionsException();
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}
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this.verbose = verbose;
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this.fileToWatch = fileToWatch;
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this.command = command;
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}
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public static Options parseCommandLineOptions(final String[] args) {
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boolean verbose = false;
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Path fileToWatch = null;
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String command = null;
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int unnamedPos = 0;
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for (final String arg : args) {
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if (arg.equals("-v")) {
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verbose = true;
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} else {
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if (unnamedPos == 0) {
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fileToWatch = Paths.get(System.getProperty("user.dir")).resolve(arg).normalize();
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} else if (unnamedPos == 1) {
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command = arg;
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} else {
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throw new IllegalCommandLineOptionsException(); // too many args
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}
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++unnamedPos;
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}
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}
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return new Options(verbose, fileToWatch, command);
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}
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public String getCommand() {
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return command;
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}
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public Path getFileToWatch() {
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return fileToWatch;
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}
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public boolean isVerbose() {
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return verbose;
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}
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}

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