紧凑版的grep

grep2.cs

/*
紧凑版的grep，相对于对象健身操的实现，这段代码只是原版本的三分之一，个人感觉可读性也不是太差。
原文地址：https://gist.github.com/1738383
*/
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.IO;
using System.Threading.Tasks;

namespace Gerp2
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length != 2)
            {
                Console.WriteLine("Usage:grep <searchPattern> <filePattern>");
                Console.WriteLine(@"Example: grep \d+ d:\code\*.py");
                return;
            }

            string searchPattern = args[0], filePath = args[1], 
                dirName = Path.GetDirectoryName(filePath), filePattern = Path.GetFileName(filePath);
            DirectoryInfo dir = new DirectoryInfo(string.IsNullOrEmpty(dirName) ? Directory.GetCurrentDirectory() : dirName);
            Regex searchRegex = new Regex(searchPattern, RegexOptions.IgnoreCase);

            var files = GetFiles(filePattern, dir);
            Parallel.ForEach(files, file => {
                Grep(file, searchRegex);
            });
        }

        static IEnumerable<FileInfo> GetFiles(string filePattern, DirectoryInfo currentDir)
        {
            var currentDirFiles = currentDir.GetFiles(filePattern);
            foreach (FileInfo file in currentDirFiles)
            {
                yield return file;
            }

            var subDirs = currentDir.GetDirectories();
            foreach (var subDir in subDirs)
            {
                var subDirFiles = GetFiles(filePattern, subDir);
                foreach (var file in subDirFiles)
                {
                    yield return file;
                }
            }
        }

        static void Grep(FileInfo file, Regex searchRegex)
        {
            using (StreamReader reader = new StreamReader(file.FullName))
            {
                int lineNo = 0;
                while (true)
                {
                    string line = reader.ReadLine();
                    if (line == null)
                        return;
                    lineNo++;

                    if (!searchRegex.IsMatch(line))
                        continue;
                    
                    Console.WriteLine("{0}({1}):{2}", file.FullName, lineNo, line);
                }
            }
        }
    }
}