A command-line grep-like program.


/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND 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.
 * 
 * Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */
import java.util.regex.*;
import java.io.*;

/** A command-line grep-like program. No options, but takes a pattern
 * and an arbitrary list of text files.
 */
public class Grep1 {
  /** The pattern we're looking for */
  protected Pattern pattern;
  /** The matcher for this pattern */
  protected Matcher matcher;

  /** Main will make a Grep object for the pattern, and run it
   * on all input files listed in argv.
   */
  public static void main(String[] argv) throws Exception {

    if (argv.length < 1) {
        System.err.println("Usage: Grep1 pattern [filename]");
        System.exit(1);
    }

    Grep1 pg = new Grep1(argv[0]);

    if (argv.length == 1)
      pg.process(new BufferedReader(new InputStreamReader(System.in)),
        "(standard input)", false);
    else
      for (int i=1; i<argv.length; i++) {
        pg.process(new BufferedReader(new FileReader(argv[i])),
          argv[i], true);
      }
  }

  /** Construct a Grep1 program */
  public Grep1(String patt) {
    pattern = Pattern.compile(patt);
    matcher = pattern.matcher("");
  }

  /** Do the work of scanning one file
   * @param ifile BufferedReader object already open
   * @param fileName String Name of the input file
   * @param printFileName Boolean - true to print filename
   * before lines that match.
   */
  public void process(
    BufferedReader inputFile, String fileName, boolean printFileName) {

    String inputLine;

    try {
      while ((inputLine = inputFile.readLine()) != null) {
        matcher.reset(inputLine);
        if (matcher.lookingAt()) {
          if (printFileName) {
            System.out.print(fileName + ": ");
          }
          System.out.println(inputLine);
        }
      }
      inputFile.close();
    } catch (IOException e) { System.err.println(e); }
  }
}
Related examples in the same category

1.	Grep0 - Match lines from stdin against the pattern on the command line.
2.	A grep-like program using NIO but NOT LINE BASED.
3.	Another Grep
A command-line grep-like program. : Grep « Regular Expressions « Java

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