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 }