001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.util;
019
020import java.io.IOException;
021import java.io.PrintStream;
022
023import org.apache.hadoop.classification.InterfaceAudience;
024import org.apache.hadoop.classification.InterfaceStability;
025import org.apache.hadoop.conf.Configuration;
026
027/**
028 * A utility to help run {@link Tool}s.
029 * 
030 * <p><code>ToolRunner</code> can be used to run classes implementing 
031 * <code>Tool</code> interface. It works in conjunction with 
032 * {@link GenericOptionsParser} to parse the 
033 * <a href="{@docRoot}/../hadoop-project-dist/hadoop-common/CommandsManual.html#Generic_Options">
034 * generic hadoop command line arguments</a> and modifies the 
035 * <code>Configuration</code> of the <code>Tool</code>. The 
036 * application-specific options are passed along without being modified.
037 * </p>
038 * 
039 * @see Tool
040 * @see GenericOptionsParser
041 */
042@InterfaceAudience.Public
043@InterfaceStability.Stable
044public class ToolRunner {
045 
046  /**
047   * Runs the given <code>Tool</code> by {@link Tool#run(String[])}, after 
048   * parsing with the given generic arguments. Uses the given 
049   * <code>Configuration</code>, or builds one if null.
050   * 
051   * Sets the <code>Tool</code>'s configuration with the possibly modified 
052   * version of the <code>conf</code>.  
053   * 
054   * @param conf <code>Configuration</code> for the <code>Tool</code>.
055   * @param tool <code>Tool</code> to run.
056   * @param args command-line arguments to the tool.
057   * @return exit code of the {@link Tool#run(String[])} method.
058   */
059  public static int run(Configuration conf, Tool tool, String[] args) 
060    throws Exception{
061    if(conf == null) {
062      conf = new Configuration();
063    }
064    GenericOptionsParser parser = new GenericOptionsParser(conf, args);
065    //set the configuration back, so that Tool can configure itself
066    tool.setConf(conf);
067    
068    //get the args w/o generic hadoop args
069    String[] toolArgs = parser.getRemainingArgs();
070    return tool.run(toolArgs);
071  }
072  
073  /**
074   * Runs the <code>Tool</code> with its <code>Configuration</code>.
075   * 
076   * Equivalent to <code>run(tool.getConf(), tool, args)</code>.
077   * 
078   * @param tool <code>Tool</code> to run.
079   * @param args command-line arguments to the tool.
080   * @return exit code of the {@link Tool#run(String[])} method.
081   */
082  public static int run(Tool tool, String[] args) 
083    throws Exception{
084    return run(tool.getConf(), tool, args);
085  }
086  
087  /**
088   * Prints generic command-line argurments and usage information.
089   * 
090   *  @param out stream to write usage information to.
091   */
092  public static void printGenericCommandUsage(PrintStream out) {
093    GenericOptionsParser.printGenericCommandUsage(out);
094  }
095  
096  
097  /**
098   * Print out a prompt to the user, and return true if the user
099   * responds with "y" or "yes". (case insensitive)
100   */
101  public static boolean confirmPrompt(String prompt) throws IOException {
102    while (true) {
103      System.err.print(prompt + " (Y or N) ");
104      StringBuilder responseBuilder = new StringBuilder();
105      while (true) {
106        int c = System.in.read();
107        if (c == -1 || c == '\r' || c == '\n') {
108          break;
109        }
110        responseBuilder.append((char)c);
111      }
112  
113      String response = responseBuilder.toString();
114      if (response.equalsIgnoreCase("y") ||
115          response.equalsIgnoreCase("yes")) {
116        return true;
117      } else if (response.equalsIgnoreCase("n") ||
118          response.equalsIgnoreCase("no")) {
119        return false;
120      }
121      System.err.println("Invalid input: " + response);
122      // else ask them again
123    }
124  }
125}