Java, Mac et parfois plus …

import org.apache.regexp.*;
import java.util.*;
import java.io.*;

/**
 * So as to test it run %JAVA_HOME%\bin\java -classpath .;jakarta-regexp.jar StringTool 2
 */
public class grep {
	public static String[] split(String source, String regexp) {
		RE re = new RE(regexp);
		return re.split(source);
	}

	public static String[] grep(Object[] sources, String regexp) {
		RE re = new RE(regexp);
		return re.grep(sources);
	}

	public static boolean match(String source, String regexp) {
		RE re = new RE(regexp);
		return re.match(source);
	}

	public static void main(String[] argv) {
		try {
			if(argv.length == 2) {
				//File f = new File(argv[1]);
				//FileReader r = new FileReader(new File(argv[1]));
				FileReader in = new FileReader(new File(argv[1]));
				BufferedReader r = new BufferedReader(in);
				String line = r.readLine();
				while(line != null) {
					if(match(line, argv[0])) System.out.println(line);
					line = r.readLine();
				}
				r.close();

			} else {
				System.out.println("Usage: grep regexp file");
			}
		} catch(Exception e) {
			e.printStackTrace();
		}
	}
}

Java