Scriptster: C# as a scripting language

I love Python! Unlike the vast majority of script languages that evolved ad-hoc, Python was built in a controlled way and has features, syntax, and runtime which click together.

I learned it at Google, got readability in it (http://1-800-magic.blogspot.com/2008/01/after-8-months-no-longer-noogler.html, and have written a few thousand lines of code since. I must say that of all the scripting languages, Python is probably the most amenable to writing thousand-plus line programs (maybe with the exception of Ruby).

As far as I am concerned, it would be nice if all other command interpreter scripting died (sorry, PowerShell) and Python were integrated into shells everywhere.

There is one problem with Python, however - it is yet another language to learn, and yet another development/runtime environment to maintain. Its integration with Windows is good, but not nearly as good as C# which was literally made for Windows. And so after I came back to Microsoft (http://1-800-magic.blogspot.com/2008/06/back-to-microsoft.html) and found myself doing most things in C# and C++, I started getting more and more rusty with Python.

Of course, being a dev manager does not help - my opportunities to code are few and far between.

What that meant that scripting became harder and harder. Soon I found myself writing small executables in C# instead of scripts. Which was all good, except that you end up with two things - a source file and an executable, which now need to be maintained together, checked in together, etc. And for very small things, it's a considerable overhead.

And then I had an idea. .NET, you see, ships with a C# compiler in the box - it is present on every (updated) Windows system. What if I were to write a small program, a C# "interpreter" of sorts, that would run C# programs directly from a command line as if they were batch files?

And so Scriptster was born.

Scriptster is a single executable that allows you to run C# programs directly, without manually compiling them. It automatically compiles C# code before running (and caches the compiled versions so the next execution is faster), but to the user it is completely transparent. It is fast, too - even the first, compiling, invocation takes fractions of a second. Subsequent runs are instantaneous.

Scripter is copy-deployable: simply copy it into a directory of your choice, run

    scriptster --install

(from a command prompt started with administrator privileges - "Run as Administrator"), and close and reopen CMD windows where you expect to be using it (CMD needs update to PATHEXT environment variable, which it reads on load).

After this, you can author and run C# scripts. For example, open Notepad, and type the following:

using System;

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("This program was invoked with the following command line parameters:");
        foreach(string s in args)
            Console.WriteLine("{0}", s);
    }
}

Save this file as testscript.csscript (the files need to have .csscript extension to work with Scriptster), and you can run it directly from the command line:

    c:\temp> testscript Blah blah blah
    This program was invoked with the following command line parameters:
    Blah
    blah
    blah

You can run considerably more involved scripts with Scriptster of course, in fact, any C# program can be run, as long as it is (1) in one file, and (2) only relies on assemblies in GAC.

Here's an example of a program that queries LDAP for user alias:

//#ref System.DirectoryServices.dll
using System;
using System.Collections.Generic;
using System.DirectoryServices;
using System.Text;

class Program
{
    static void Main(string[] args)
    {
        DirectorySearcher ds = new DirectorySearcher();

        ds.PropertiesToLoad.Add("mail");

        foreach (string alias in args)
        {
            ds.Filter = "(SAMAccountName=" + alias + ")";
            SearchResult result = ds.FindOne();
            if (result == null)
            {
                Console.Error.WriteLine("Could not resolve {0}", alias);
                continue;
            }
            Console.WriteLine("{0}'s email is {1}", alias,
                result.Properties["mail"][0].ToString());
        }
    }
}

Notice "//#ref" at the top of the file? This is how you tell Scriptster about referenced assembly.

You can edit scripts in Visual Studio, debug them, then rename the files to .csscript extensions and run them right from the command line. You can take existing small programs, and run them from the command line, too.

Interested? You can download Scriptster, including the source code, from CodePlex: http://scriptster.codeplex.com.

Give it a whirl, and let me know how it works out.