Convert Oracle "RR" date formats to SQL Server "YYYY" formats

program.cs

namespace OracleRRConverter
{
    // Takes an Oracle-generated SQL script file and converts something like
    // to_date('02.10.18','DD.MM.RR') to something like CONVERT(DATETIME,'02.10.2018',126).
    // https://dba.stackexchange.com/q/244722/42

    using System;
    using System.Collections.Generic;
    using System.IO;
    using System.Linq;
    using System.Text;
    using System.Text.RegularExpressions;

    internal static class Program
    {
        private static int Main(string[] args)
        {
            var sourcePath = args[0];
            if (string.IsNullOrEmpty(sourcePath))
            {
                Console.Error.WriteLine(@"No file or directory path as first argument specified.");
                return -1;
            }

            var sourceFilePaths = new List<string>();

            if (Directory.Exists(sourcePath))
            {
                sourceFilePaths.AddRange(Directory.GetFiles(sourcePath, @"*.sql"));
            }
            else if (File.Exists(sourcePath))
            {
                sourceFilePaths.Add(sourcePath);
            }
            else
            {
                Console.Error.WriteLine($@"File or directory path '{sourcePath}' does not exist.");
                return -1;
            }

            if (sourceFilePaths.Count <= 0)
            {
                Console.Error.WriteLine(@"No .sql files found/specified.");
                return -1;
            }

            var sourceFolderPath = Path.GetDirectoryName(sourceFilePaths.First());
            var backupFolderPath = Path.Combine(sourceFolderPath, $@"backups\{DateTime.Now.Ticks}");
            Directory.CreateDirectory(backupFolderPath);

            foreach (var sourceFilePath in sourceFilePaths)
            {
                Console.WriteLine($@"Processing file '{sourceFilePath}'.");

                var sourceFileName = Path.GetFileName(sourceFilePath);
                var sourceFileNameWithoutExtensions = Path.GetFileNameWithoutExtension(sourceFilePath);
                var sourceFileExtension = Path.GetExtension(sourceFilePath);

                var backupFilePath = Path.Combine(backupFolderPath,
                    $@"{sourceFileName}");
                var tempFilePath = Path.Combine(sourceFolderPath,
                    $@"{sourceFileNameWithoutExtensions}.temp.{Guid.NewGuid():N}{sourceFileExtension}");

                var ec = Encoding.Default;

                using (var reader = new StreamReader(sourceFilePath, ec))
                using (var writer = new StreamWriter(tempFilePath, false, ec))
                {
                    var regEx = new Regex(@"to_date\('(\d\d)\.(\d\d)\.(\d\d)','DD\.MM\.RR'\)", RegexOptions.Compiled);

                    while (reader.Peek() > 0)
                    {
                        var line = reader.ReadLine();

                        if (string.IsNullOrEmpty(line) || !regEx.IsMatch(line))
                        {
                            writer.WriteLine(line);
                        }
                        else
                        {
                            var newLine = line;

                            // Do some action with the string.
                            var match = regEx.Match(newLine);
                            while (match.Success)
                            {
                                var day = Convert.ToInt32(match.Groups[1].Value);
                                var month = Convert.ToInt32(match.Groups[2].Value);
                                var rr = Convert.ToInt32(match.Groups[3].Value);

                                var year = rr <= 49 ? 2000 + rr : 1900 + rr;

                                var replacement = $@"CONVERT(DATETIME,'{year:D4}-{month:D2}-{day:D2}',126)";

                                newLine =
                                    newLine.Substring(0, match.Index) +
                                    replacement +
                                    newLine.Substring(match.Index + match.Length);

                                match = regEx.Match(newLine);
                            }

                            writer.WriteLine(newLine);
                        }
                    }
                }

                File.Move(sourceFilePath, backupFilePath);
                File.Move(tempFilePath, sourceFilePath);
            }

            return 0;
        }
    }
}