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 }