grep.java

java实现正则表达式的代码

/*
 * $Id: grep.java,v 1.7 2003/11/07 20:16:23 dfs Exp $
 *
 * ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2000 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation", "Jakarta-Oro" 
 *    must not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact [e-mail].
 *
 * 5. Products derived from this software may not be called "Apache" 
 *    or "Jakarta-Oro", nor may "Apache" or "Jakarta-Oro" appear in their 
 *    name, without prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */


package examples;

import java.io.*;
import java.util.*;

import org.apache.oro.text.*;
import org.apache.oro.text.regex.*;

/**
 * This is a no-frills implementation of grep using Perl regular expressions.
 * You can easily add most of the options present in most grep versions by
 * creating a MatchAction class or classes whose behavior varies based on
 * the provided flags.
 *
 * @version @version@
 */
public final class grep {
  static int _file = 0;

  // args[] is declared final so that Inner Class may reference it.
  public static final void main(final String[] args) {
    MatchActionProcessor processor = new MatchActionProcessor();

    if(args.length < 2) {
      System.err.println("Usage: grep <pattern> <filename>");
      System.exit(1);
    }

    try {
      if(args.length > 2) {
	// Print filename before line if more than one file is specified.
	// Rely on _file to point to current file being processed.
	processor.addAction(args[0], new MatchAction() {
	  public void processMatch(MatchActionInfo info) {
	    info.output.println(args[_file] + ":" + info.line);
	  }
	});
      } else {
	// We rely on the default action of printing matched 
	// lines to the given OutputStream
	processor.addAction(args[0]);
      }
    } catch(MalformedPatternException e) {
      System.err.println("Bad pattern.");
      e.printStackTrace();
      System.exit(1);
    }

    for(_file = 1; _file < args.length; _file++) {
      try {
	processor.processMatches(new FileInputStream(args[_file]), System.out);
      } catch(IOException e) {
	System.err.println("Error opening or reading " + args[_file]);
	e.printStackTrace();
	System.exit(1);
      }
    }
  }

}