by Miguel de Icaza

Funkists, why does System.IO.Stream not have a CopyStream method, it seems like everyone ends up implementing this.


Posted on 24 Sep 2008

Love World Domination!

by Miguel de Icaza

Chris Anderson is wearing a Mono T-Shirt on this PDC interview and is hosted on DekiWiki, a Mono-powered Wiki site.

This is clearly awesome.

In other news, the awesome hackers at Imendio have officially released Gtk+ for OSX packages.

Posted on 24 Sep 2008


by Miguel de Icaza

Kudos to Ben and the rest of the Captcha team.

Today I downloaded the binaries for reCaptcha.NET for a web page that I was setting up and it worked out of the box. No recompiles necessary:

  • Drop the Recaptcha.dll in the bin directory of the ASP.NET app.
  • Get your public/private key.
  • Insert this in your page:
  • Hit refresh. Ta da!

Posted on 17 Sep 2008

Encrypted File Systems

by Miguel de Icaza

I just found out about encfs, a user-space encrypted file system that runs on top of FUSE.

To use it, just type:

	$ encfs ~/.encryptedstorage ~/secure

And follow the directions. You then will have a ~/secure directory where you can stash all the material that you would not want to become public if you were to lose your laptop.

But it gets better than this. You can use sshfs to store files on a remote server, and then use the sshfs-backed file system as your encrypted storage, you can then keep your files stashed on a remote server, completely encrypted.

Posted on 16 Sep 2008

Mono team, hiring again

by Miguel de Icaza

Hey folks, it is that time of the year when we are looking to hire some developers to work on Mono.

We are looking for people with experience in Linux, with experience building software from source code and good C# or Java skills. Experience with ASP.NET and ADO.NET is a plus.

The positions this time are only available in Boston, if you are interested, send me an email.

Update: we have filled this position.

Posted on 15 Sep 2008

Securing a Unix Domain Socket: Looking for Help

by Miguel de Icaza

There is a cool hack that we want to introduce in Mono that would allow a remote process to debug a examine data in a running Mono instance. The hack uses the embeddable compiler.

The proposed extension to Mono would use a socket on /tmp/mono-USER/.mono-PID created by the Mono process and set the permissions to read/write for the owner and nothing for the group or other users.

What can go wrong security-wise with the above setup? What should we check that is not immediately obvious?

So far:

  • Create directory with 0600 permissions, bail if mkdir returns anything but 0.
  • Create socket in directory; It should be safe at this point, and change the permissions of the socket (is this really needed?).

Posted on 15 Sep 2008

Credit where credit is due

by Miguel de Icaza

The csharp interactive shell and the embeddable compiler hacks could only have been possible thanks to the work that Marek Safar has put into implementing C# 3.0, cleaning up the compiler and laying down the foundation for a reusable compiler.

Some time ago, our regression test suite for the compiler was taking 20-30 minutes to run. Marek refactored the compiler so that we could reuse the same instance without launching a new process for each of our 1,500 individual tests.

Without Marek's dedication and love for the compiler, we would never have gotten here.

Posted on 11 Sep 2008

C# Eval: An Embeddable Compiler

by Miguel de Icaza

Hello Internets and C# Lovers!

After the C# Interactive Shell started working, it became obvious that we now had C#'s eval and that it would be incredibly interesting to enable people to embed a C# Eval in their application.

I did a little bit of refactoring on the codebase last night, and now we expose a few methods that allow developers to evaluate C# expressions and statements dynamically.

Usage is very simple, you must reference the `gmcs.exe' assembly, this contains the C# Eval, then you invoke the CSharpEvaluator.Evaluate method, and get the results back.

The following is a small command line calculator that takes C# expressions:

using Mono.CSharp;
using System;

class MyCalculator {
	static void Main (string [] args)
		Console.WriteLine (CSharpEvaluator.Evaluate (args [0] + ";"));

Compile the above, and execute:

$ mono calculator.exe '1+2'

There are a number of overload methods for Evaluate that give more control over how things are evaluated. The csharp command is now written entirely using the CSharpEvaluator API. The code is now pretty simple: pretty printing of values, dealing with partial input, loading startup files (if any) and import the default namespaces.

A few uses that come to mind:

  • Use C# as a scripting language for your application.
  • Use it for startup scripts of your own application (similar to .emacs, but with C# instead).
  • Use it to explore the state of your application live.
  • Use it to debug your application as it is running.
  • Embed the compiler on Silverlight and run C# on your web browser, similar to how Jimmy did it for Ruby.
  • Embed it into your app and expose it as a service that you can connect to, and do it live!

The four or five public methods of the API are documented in the source using C# doc tags. When Mono 2.2 goes out, we will publish docs for them.

As we announced back in April, Mono's C# compiler is now licensed under the MIT X11 license, so you can embed at will.


Joe Shaw mentioned a few days ago that it would be nice to support something like Twisted's Manhole where your application is listening on a port and then you can connect to it and debug it. It should take a dozen lines to write it, but I am heading out for dinner now.

But if I were to do it, I would probably make the csharp command (all 240 lines of it) support a --server command line option and have it connect to the server and send strings over the wire instead of executing locally. That way you get to use the awesome getline.cs command line editor and history locally and let the server run the code.

Getting Your Hands on This

To enjoy this hack, you have to either wait for Mono 2.2 or install Mono from SVN, all of the code is checked in.

Update: Clarification

Since it was not obvious, we do support C# 3.0, which includes the entire LINQ stack in the above expression evaluator:

using Mono.CSharp;
using System.Collections;
using System;

class X {
	static void Main (string [] args)
		Evaluator.Run ("using System; using System.Linq;");
		bool ress;
		object res;
		string s = Evaluator.Evaluate (
			"from x in System.IO.Directory.GetFiles (\"/etc\") where x.Length < 10 select x;",
			out res, out ress);

		foreach (var v in (IEnumerable) res){
			Console.Write (v);
			Console.Write (' ');

The above uses a LINQ expression, and this is the result in my system (files whose full pathname is less than 10 characters):

/etc/motd /etc/mtab /etc/raw /etc/rpc 

Posted on 10 Sep 2008

Enterprise Library 4.0 now Open Source

by Miguel de Icaza

Hello Internets!

Some very good news: As part of the ongoing discussion on the MS Limited Permissive License, I was doing some Google searches on it and came across the Enterprise Library 4.0 release.

Enterprise Library was a project that came out of the Patterns and Practices group at Microsoft, and they had historically used licenses that were not open source friendly. This new release is now licensed under the terms of the open-source friendly MS-PL license.

In the past, various people have asked us to implement an open source version of it, so they could use those building blocks on Unix with Mono. We never had any spare cycles to look into this, so the blocks provided by Enterprise Library were always beyond Mono users.

As it turns out, since May 2008 it has been possible to use the library with Mono on non-Windows platforms.

Now all there is left to do is to package it in a convenient form.

Posted on 09 Sep 2008

Interactive C# Shell

by Miguel de Icaza

During the last HackWeek, I had a chance to work on a project that we had been discussing in the Mono team: an interactive C# shell.

The idea was simple: create an interactive C# shell by altering the compiler to generate and execute code dynamically as opposed to merely generating static code.

The result is the csharp command. The command provides an read-eval-print loop for entering C# statements and expressions:

	csharp> 1;
	csharp> "Hello, World".IndexOf (",");
	csharp> Console.WriteLine ("Hello");

Statements are executed; Expressions are evaluated, and the result displayed. There is support for rendering arrays, IEnumerables and dictionaries specially, consider the following C# 3 declaration:

	csharp> new Hashtable () { { "/bin", "executable files" }, { "/etc", "configuration files" } };

You will get this back when rendered:

	{{ "/tmp", "Temporary files" }, { "/bin", "executable files" }}

Statements can span multiple lines; In those cases the interactive shell will use a different prompt to indicate that more input is expected, for example:

	csharp> 1 +
	      > 2;

One of the main advantages of this shell is that you can try out your LINQ expressions directly on the shell, for example, the following query works on the result from Directory.GetFiles:

	csharp> using System.IO;
	csharp> var last_week = DateTime.Now - TimeSpan.FromDays (7);
	csharp> from f in Directory.GetFiles ("/etc") 
	      >    let fi = new FileInfo (f)
	      >    where fi.LastWriteTime < last_week
              >      select f;
        { "/etc/adjtime", "/etc/asound.state", "/etc/",
	"/etc/mtab", "/etc/printcap", "/etc/resolv.conf" }

The LINQ expressions are not limited to working on IEnumerables, you can also use LINQ to XML or LINQ to any database provider supported by Mono by loading the assembly:

	csharp> LoadLibrary ("System.Xml.Linq");
	csharp> using System.Xml.Linq;
	csharp> var xml = new XElement("CompilerSources",
	      >   from f in Directory.GetFiles ("/cvs/mcs/mcs")
	      >   let fi = new FileInfo (f)
	      >   orderby fi.Length
	      >  select new XElement ("file", new XAttribute ("name", f), new XAttribute ("size", fi.Length)));
	csharp> xml;
	  <file name="/cvs/mcs/mcs/mcs.exe.config" size="395" />
	  <file name="/cvs/mcs/mcs/gmcs.exe.config" size="464" />
	  <file name="/cvs/mcs/mcs/OPTIMIZE" size="498" />
	  <file name="/cvs/mcs/mcs/lambda.todo" size="658" />
	  <file name="/cvs/mcs/mcs/smcs.exe.sources" size="726" />

A differences between csharp and the C# language is that I felt that for interactive use, it would be important to change the type of a variable, so the following is allowed:

	csharp> var a = 1;
	csharp> a;
	csharp> a.GetType ();
	csharp> var a = "Foo";
	csharp> a;
	csharp> a.GetType ();

To load code interactive I added two methods: LoadAssembly and LoadPackage.

LoadAssembly is the equivalent of passing the -r command line argument to csharp or mcs, this example shows System.Xml.Linq in use:

csharp> LoadAssembly ("System.Xml.Linq");
csharp> using System.Xml.Linq;
csharp> XDocument doc = new XDocument(
      >     new XDeclaration("1.0", "utf-8", "yes"),
      >     new XComment("Sample RSS Feed"),
      >     new XElement("rss", 
      >         new XAttribute("version", "2.0"),
      >         new XElement ("channel",
      >             new XElement("title", "RSS Channel Title"),
      >             new XElement("description", "RSS Channel Description."),
      >             new XElement("link", ""),
      >             new XElement("item",
      >                 new XElement("title", "First article title"),
      >                 new XElement("description", "First Article Description"),
      >                 new XElement("pubDate", DateTime.Now.ToUniversalTime()),
      >                 new XElement("guid", Guid.NewGuid())),
      >             new XElement("item",
      >                 new XElement("title", "Second article title"),
      >                 new XElement("description", "Second Article Description"),
      >                 new XElement("pubDate", DateTime.Now.ToUniversalTime()),
      >                 new XElement("guid", Guid.NewGuid()))
      >             )
      >         )
      >      );

The variable doc is then rendered:

csharp> doc;
<?xml version="1.0" encoding="utf-16" standalone="yes"?>
<!--Sample RSS Feed-->
<rss version="2.0">
    <title>RSS Channel Title</title>
    <description>RSS Channel Description.</description>
      <title>First article title</title>
      <description>First Article Description</description>
      <pubDate>9/8/2008 5:13:34 PM</pubDate>
      <title>Second article title</title>
      <description>Second Article Description</description>
      <pubDate>9/8/2008 5:13:34 PM</pubDate>


LoadPackage is the equivalent of invoking the compiler with the -pkg: flag. This is a Mono-ism that integrates Mono libraries with Unix's pkg-config. Packages allow definitions and multiple assemblies to be loaded in a single call, for example, this loads the Gtk# 2.0 package:

	csharp> LoadPackage ("gtk-sharp-2.0");
	csharp> using Gtk;
	csharp> Application.Init ();
	csharp> var b = new Button ("Hello Interactive Shell");
	csharp> var w = new Window ("So cute!");
	csharp> b.Clicked += delegate { Application.Quit (); };
	csharp> w.Add (b);
	csharp> w.ShowAll ();
	csharp> Application.Run ();


This shell has been incredibly useful to debug things in the last few weeks, as it avoids the tedious typing to try out APIs and to see what some function might return. Launch csharp and test things away.

To improve the experience of the command line editing, I wrote a managed readline replacement, it provides history, keyboard navigation and searching.

Also the System, System.Linq, System.Collections, and System.Collections.Generic namespaces are imported by default.

Additionally, the csharp command will load any assemblies and C# scripts that you have in the ~/.config/csharp directory. If you are working constantly say on LINQ, you can put there all of your using and LoadLibrary statements.


The csharp command will be available in Mono 2.2, which is still a few months away, or it can be obtained by compiling Mono from SVN today.

Interactive Commands

Currently there are a few static methods and properties that you can invoke from the command line, like the "help" property that will display some help, and the "quit" property that terminates the shell as well as things like LoadLibrary and LoadPackage that I have described before. A complete list is available on the CsharpRepl page.

I am interested in hearing which other features should be added to the shell. I think we need some special commands to describe types and objects, like monop.

Additionally, currently values are displayed by using ToString(), but perhaps we need a method Inspect(object) that would show the values of all public fields and properties, like a debugger would.

Which other commands should be added?

Posted on 08 Sep 2008

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