====== touch ======

A small C# utility to modify a file's timestamp. Requires a filename and timestamp in the form //YYYYMMDDHHMMSS//; e.g. to update the timestamp of ''myfile,txt'' to 13:30:29 on 10-Mar-2018, use:
<code dos>touch myfile.txt 20180310133029</code>

===== Implementation =====
Visual Studio solution available [[https://github.com/richardswinbank/touch|on GitHub]]. Really just this inside your main program class:

<code csharp>static void Main(string[] args)
{
  try
  {
    if (args.Length != 2)
      throw new TouchException("touch usage: touch <filename> <timestamp>");
    var filename = args[0];
    if (!File.Exists(filename))
      throw new TouchException("touch: file \"" + filename + "\" not found");

    DateTime mt = ParseTimestamp(args[1]);
    Console.WriteLine("Set last modified time of \"" + filename + "\" to " + mt.ToString("dd MMM yyyy HH:mm:ss") + "? (Y to apply)");
    if (Console.ReadKey(true).Key == ConsoleKey.Y)
    {
      File.SetLastWriteTime(filename, mt);
      Console.WriteLine("Timestamp updated");
      return;
    }
    Console.WriteLine("No changes made");
  }
  catch (TouchException e)
  {
    Console.WriteLine(e.Message);
    Environment.Exit(1);
  }
  catch (Exception e)
  {
    Console.WriteLine(e.StackTrace);
    Environment.Exit(2);
  }
}

private static DateTime ParseTimestamp(string ts)
{
  return new DateTime(
      ParseInt(ts, 0, 4)
    , ParseInt(ts, 4, 2)
    , ParseInt(ts, 6, 2)
    , ParseInt(ts, 8, 2)
    , ParseInt(ts, 10, 2)
    , ParseInt(ts, 12, 2)
    );
}

private static int ParseInt(string ts, int off, int len)
{
  try
  {
    return int.Parse(ts.Substring(off, len));
  }
  catch (FormatException)
  {
    InvalidTimestamp(ts);
  }
  catch (ArgumentOutOfRangeException)
  {
    InvalidTimestamp(ts);
  }
  return -1;  // never reached
}

private static void InvalidTimestamp(string ts)
{
  throw new TouchException("touch: invalid timestamp: " + ts);
}

private class TouchException : Exception
{
  public TouchException(string message) : base(message)
  {
  }
}
</code>



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