Java Grep Library

Question

Is there any good, simple Java Grep Library? I\'m not opposed to native code, or scripting, and I\'ll do it, but for my purposes, throughput is not a huge deal, and it would

Answer 1

yep. Grep4j - a grep lib for Unix environments, and you can also grep remotely easy : http://code.google.com/p/grep4j/

Answer 2

String.matches(someRegex); Internally uses java.util.regex.Pattern and Matcher

Answer 3

Unix4j also implements a (pure java) grep command: http://www.unix4j.org

Unix4j.fromStrings("1:A", "2:B", "3:AB", "4:AC", "5:ABC").toFile("myFile.txt");
Unix4j.fromFile("myFile.txt").grep("AB").toStdOut();

>>>
3:AB 
5:ABC

Disclaimer: I am one of the contributors to the unix4j project.

Answer 4

I'm not aware of a sophisticated grep librarystrong text, but you are right: it's not hard to write. I suggest a combination of commons-io and String.matches(someRegex):

public class Grep extends DirectoryWalker
{
    public Grep(){
        super();
    }

    public List clean(File startDirectory){
      List results = new ArrayList();
      walk(startDirectory, results);
      return results;
    }

    protected boolean handleDirectory(File directory,
                                      int depth, Collection results){
      // Decide if a (sub) directory will be handled for recursive search
      return true;
    }

    protected void handleFile(File file, int depth, Collection results)
    {
        LineIterator it = FileUtils.lineIterator(file, "UTF-8");
        try{
            while (it.hasNext()){
                String line = it.nextLine();
                if(line.matches("myRegEx")){
                    results.add(file);
                }
            }
         }
         finally {LineIterator.closeQuietly(it);}
    }
}

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Update Marco pointed out Unix4j which is a quite interesting library which emulates the unix pipelining | with Java method chaining. grep is supported as well as cat, cd, cut, echo, find, grep, head, ls, sed, sort, tail, uniq, wc, barges.