1 /*
   2  * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.jfr.internal.tool;
  27 
  28 import java.io.PrintStream;
  29 import java.util.Arrays;
  30 import java.util.Collections;
  31 import java.util.Deque;
  32 import java.util.List;
  33 
  34 final class Help extends Command {
  35 
  36     @Override
  37     public String getName() {
  38         return "help";
  39     }
  40 
  41     @Override
  42     public List<String> getOptionSyntax() {
  43         return Collections.singletonList("[<command>]");
  44     }
  45 
  46     protected List<String> getAliases() {
  47         return Arrays.asList("--help", "-h", "-?");
  48     }
  49 
  50     @Override
  51     public void displayOptionUsage(PrintStream stream) {
  52         println("  <command>   The name of the command to get help for");
  53     }
  54 
  55     @Override
  56     public String getDescription() {
  57         return "Display all available commands, or help about a specific command";
  58     }
  59 
  60     @Override
  61     public void execute(Deque<String> options) throws UserSyntaxException, UserDataException {
  62         if (options.isEmpty()) {
  63             Command.displayHelp();
  64             return;
  65         }
  66         ensureMaxArgumentCount(options, 1);
  67         String commandName = options.remove();
  68         Command c = Command.valueOf(commandName);
  69         if (c == null) {
  70             throw new UserDataException("unknown command '" + commandName + "'");
  71         }
  72         println(c.getTitle());
  73         println();
  74         c.displayUsage(System.out);
  75     }
  76 }