code: /*
  * Copyright 2014 Basis Technology Corp.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
  package com.basistech.tclre;
  
  import com.google.common.base.Charsets;
  import com.google.common.io.CharSource;
  import com.google.common.io.Files;
  import org.kohsuke.args4j.Argument;
  import org.kohsuke.args4j.CmdLineException;
  import org.kohsuke.args4j.CmdLineParser;
  
  import java.io.BufferedReader;
  import java.io.File;
  import java.io.IOException;
  import java.util.EnumSet;
  import java.util.List;
  
  /**
   * Grep command line to exercise the regex package.
   */
  @SuppressWarnings("PMD")
  public final class Grep {
      @Argument(required = true)
      String pattern;
      @Argument(index = 1)
      List<File> inputs;
  
      private RePattern re;
  
      private Grep() {
          //
      }
  
      public static void main(String[] args) throws IOException, RegexException {
          Grep that = new Grep();
          CmdLineParser parser = new CmdLineParser(that);
          try {
              if (args.length == 0) {
                  System.err.println("grep PATTERN file1 ... fileN");
                  parser.printUsage(System.err);
                  return;
              }
              parser.parseArgument(args);
          } catch (CmdLineException e) {
              // handling of wrong arguments
              System.err.println(e.getMessage());
              parser.printUsage(System.err);
              System.exit(1);
          }
  
          that.go();
  
      }
  
      private void go() throws IOException, RegexException {
          re = Compiler.compile(pattern, EnumSet.of(PatternFlags.EXTENDED, PatternFlags.ADVANCED));
          for (File input : inputs) {
              processFile(input);
          }
  
      }
  
      private void processFile(File input) throws IOException, RegexException {
          CharSource inputCharSource = Files.asCharSource(input, Charsets.UTF_8);
          processReader(inputCharSource.openBufferedStream());
      }
  
      private void processReader(BufferedReader bufferedReader) throws IOException, RegexException {
          String line;
          while ((line = bufferedReader.readLine()) != null) {
              processOneLine(line);
          }
      }
  
      private void processOneLine(String line) throws RegexException {
          // not trying to match yet.
      }
  }
  