Tools/javacmd

#!/usr/bin/env -S java --source 11
/*
 * BRLTTY - A background process providing access to the console screen (when in
 *          text mode) for a blind person using a refreshable braille display.
 *
 * Copyright (C) 1995-2023 by The BRLTTY Developers.
 *
 * BRLTTY comes with ABSOLUTELY NO WARRANTY.
 *
 * This is free software, placed under the terms of the
 * GNU Lesser General Public License, as published by the Free Software
 * Foundation; either version 2.1 of the License, or (at your option) any
 * later version. Please see the file LICENSE-LGPL for details.
 *
 * Web Page: http://brltty.app/
 *
 * This software is maintained by Dave Mielke <dave@mielke.cc>.
 */

import java.io.File;
import java.util.Arrays;
import java.util.ArrayList;

/* This is the class that contains the main() method.
 * Don't be misled by the fact that it seems to have a required name.
 * It can actually have any name so we chose to give it a descriptive one.
 * The only rule is that the main() method must be within the first class.
 */
public class ScriptImplementation extends ScriptHelper {
  public static void main (String[] arguments) {
    var operands = new ScriptOperands(arguments);

    String action = operands.next();
    if (action == null) syntaxError("action not specified");

    switch (action) {
      case "jvmpath": {
        verifyNoMoreParameters(operands);

        String path = getProcessInformation().command().orElse(null);
        if (path != null) putScriptOutput("%s", path);

        break;
      }

      default: {
        syntaxError("unknown action: %s", action);
      }
    }
  }
}

public class ScriptHelper {
  public static ProcessHandle.Info getProcessInformation () {
    return ProcessHandle.current().info();
  }

  public static String getScriptPath () {
    String[] arguments = getProcessInformation().arguments().orElse(null);
    if (arguments == null) return null;

    final int index = 2;
    if (arguments.length <= index) return null;
    return arguments[index];
  }

  public static File getScriptFile () {
    String path = getScriptPath();
    if (path == null) return null;
    return new File(path);
  }

  public static String getScriptName () {
    File file = getScriptFile();
    if (file == null) return null;
    return file.getName();
  }

  public static void putScriptMessage (String format, Object... arguments) {
    String message = String.format(format, arguments);
    String tag = getScriptName();

    if ((tag != null) && !tag.isEmpty()) {
      String prefix = tag + ": ";
      message = prefix + message;

      prefix = " ".repeat(prefix.length());
      message = message.replaceAll("(\n)", ("$1" + prefix));
    }

    System.err.println(message);
  }

  public static void syntaxError (String format, Object... arguments) {
    putScriptMessage(format, arguments);
    System.exit(2);
  }

  public static void putTooManyParameters () {
    syntaxError("too many parameters");
  }

  public static void verifyNoMoreParameters (ScriptOperands operands) {
    if (!operands.isEmpty()) putTooManyParameters();
  }

  public static void putScriptOutput (String format, Object... arguments) {
    System.out.println(String.format(format, arguments));
  }
}

public class ScriptOperands extends ArrayList<String> {
  public ScriptOperands (String... operands) {
    super(Arrays.asList(operands));
  }

  public String next () {
    return isEmpty()? null: remove(0);
  }
}