Capturing Output as String and Variable in Powershell

I'm embedding a posh shell into a C# app I'm writing, and I needed a way to capture the text output of the app, as well as the results as an array. This is what I came up with:

Runspace runspace = RunspaceFactory.CreateRunspace();
runspace.Open();

runspace.SessionStateProxy.SetVariable( "location", "c:\\" );
Pipeline pipeline = runspace.CreatePipeline();
pipeline.Commands.AddScript( "get-childitem $location" );

// this splits the output into the text and variable
Command cmd = new Command( "tee-object" );
// this is where the result array will end up
cmd.Parameters.Add( "variable", "invoke_results" );
pipeline.Commands.Add( cmd );
// forces the rest of the output to string
pipeline.Commands.Add( "out-string" );

Collection<PSObject> results = pipeline.Invoke();

var errors = pipeline.Error;

if( 0 < errors.Count )
{
 // there might be more. For now, we read the first
 var oneError = errors.Read( 1 );
 ConsoleColor formerConsoleColor = Console.ForegroundColor;
 Console.ForegroundColor = ConsoleColor.Red;
 Console.WriteLine( "Error: {0}", oneError[0] );
 Console.ForegroundColor = formerConsoleColor;
}
else
// hooray, no errors
{
 object[] resArray = (object[])runspace.SessionStateProxy.GetVariable( "invoke_results" );

 Func<List<String>, object, List<String>> nameAcc =
  ( n, o ) =>
  {
   n.Add( o.ToString() );
   return n;
  };

 List<String> names = resArray.AsEnumerable().Aggregate( new List<String>(),
        nameAcc
  );

 foreach( var list in names )
 {
  Console.WriteLine( list );
 }
}

runspace.Close();

This was much easier than trying to implement my own custom host.

Facebook Scalability Story

Here's a synopsis of a presentation given as part of the CNS lecture series, discussing Facebook's architecture.

Even though it is just an overview, it is pretty detailed, and gives interesting little factoids such as:

• 600k photos/sec
• php for the front end
• 30K servers, in two datacenters
• ”Work fast and don’t be afraid to break things.”

There's lots of neat stuff in there.

MS SQL Server Pivot Tables

Another one for the "don't lose me" pile...

MS SQL 2005 and onward have a PIVOT function, which acts like an Excel pivot table.

Notes here.