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     */
018    package org.apache.hadoop.util;
019    
020    import java.io.PrintStream;
021    
022    import org.apache.hadoop.classification.InterfaceAudience;
023    import org.apache.hadoop.classification.InterfaceStability;
024    import org.apache.hadoop.conf.Configuration;
025    
026    /**
027     * A utility to help run {@link Tool}s.
028     * 
029     * <p><code>ToolRunner</code> can be used to run classes implementing 
030     * <code>Tool</code> interface. It works in conjunction with 
031     * {@link GenericOptionsParser} to parse the 
032     * <a href="{@docRoot}/org/apache/hadoop/util/GenericOptionsParser.html#GenericOptions">
033     * generic hadoop command line arguments</a> and modifies the 
034     * <code>Configuration</code> of the <code>Tool</code>. The 
035     * application-specific options are passed along without being modified.
036     * </p>
037     * 
038     * @see Tool
039     * @see GenericOptionsParser
040     */
041    @InterfaceAudience.Public
042    @InterfaceStability.Stable
043    public class ToolRunner {
044     
045      /**
046       * Runs the given <code>Tool</code> by {@link Tool#run(String[])}, after 
047       * parsing with the given generic arguments. Uses the given 
048       * <code>Configuration</code>, or builds one if null.
049       * 
050       * Sets the <code>Tool</code>'s configuration with the possibly modified 
051       * version of the <code>conf</code>.  
052       * 
053       * @param conf <code>Configuration</code> for the <code>Tool</code>.
054       * @param tool <code>Tool</code> to run.
055       * @param args command-line arguments to the tool.
056       * @return exit code of the {@link Tool#run(String[])} method.
057       */
058      public static int run(Configuration conf, Tool tool, String[] args) 
059        throws Exception{
060        if(conf == null) {
061          conf = new Configuration();
062        }
063        GenericOptionsParser parser = new GenericOptionsParser(conf, args);
064        //set the configuration back, so that Tool can configure itself
065        tool.setConf(conf);
066        
067        //get the args w/o generic hadoop args
068        String[] toolArgs = parser.getRemainingArgs();
069        return tool.run(toolArgs);
070      }
071      
072      /**
073       * Runs the <code>Tool</code> with its <code>Configuration</code>.
074       * 
075       * Equivalent to <code>run(tool.getConf(), tool, args)</code>.
076       * 
077       * @param tool <code>Tool</code> to run.
078       * @param args command-line arguments to the tool.
079       * @return exit code of the {@link Tool#run(String[])} method.
080       */
081      public static int run(Tool tool, String[] args) 
082        throws Exception{
083        return run(tool.getConf(), tool, args);
084      }
085      
086      /**
087       * Prints generic command-line argurments and usage information.
088       * 
089       *  @param out stream to write usage information to.
090       */
091      public static void printGenericCommandUsage(PrintStream out) {
092        GenericOptionsParser.printGenericCommandUsage(out);
093      }
094      
095    }