1 /*
   2  * Copyright (c) 2016, 2019, 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.cmd;
  27 
  28 import java.util.Deque;
  29 
  30 final class HelpCommand extends Command {
  31 
  32     @Override
  33     public String getOptionSyntax() {
  34         return "[<command>]";
  35     }
  36 
  37     @Override
  38     public void displayOptionUsage() {
  39         println("  <command>   The name of the command to get help for");
  40         println();
  41         Command.displayAvailableCommands();
  42     }
  43 
  44     @Override
  45     public String getName() {
  46         return "help";
  47     }
  48 
  49     @Override
  50     public String getDescription() {
  51         return "Display help about a command";
  52     }
  53 
  54     @Override
  55     public void execute(Deque<String> options) {
  56         if (options.isEmpty()) {
  57             displayUsage();
  58         } else {
  59             ensureMaxArgumentCount(options, 1);
  60             String commandName = options.remove();
  61             Command c = Command.valueOf(commandName);
  62             if (c == null) {
  63                 userFailed("Unknown command " + commandName);
  64             }
  65             c.displayUsage();
  66         }
  67     }
  68 }