F# environment integration (for scripting)

Question

I like F# and I want to practice a little by writing some scripts for automation of some annoying task.

How do i interact with other programs the same way i can do from CMD or PowerShell for example RoboCopy or iisreset or net?

I know i can do it myself with System.Diagnostics.Process but it's difficult to do right (return codes, standard streams, etc.) .

There has to be a library for this, any suggestions?

Answer 1

You want to use the System.Management.Automation namespace. Here's an example of running some cmdlets from F#.

// C:\Program Files (x86)\Reference Assemblies\Microsoft\WindowsPowerShell\3.0
open System.Management.Automation
open System.Management.Automation.Runspaces;

let runSpace = RunspaceFactory.CreateRunspace()
runSpace.Open()
let pipeline = runSpace.CreatePipeline()

let getProcess = new Command("Get-Process")
pipeline.Commands.Add(getProcess)

let sort = new Command("Sort-Object")
sort.Parameters.Add("Property", "VM")
pipeline.Commands.Add(sort)

// Identical to the following PowerShell command line:
// PS > Get-Process | Sort-Object -Property VM | select ProcessName

let output = pipeline.Invoke()
for psObject in output do
    psObject.Properties.Item("ProcessName").Value.ToString()
    |> printfn "%s"

You can also build cmdlets with F# and use PowerShell to move data. Check out this post on the Visual Studio F# Team Blog. It's a good example on how to write a Cmdlet in F#. You can also embed F# into PowerShell but in general it's better to make Cmdlets.

Cmdlet MSDN reference
Scripting with Windows PowerShell

Answer 2

Fake has an ExecProcess task that might help. Also you could look at the Fake source for more ideas.

Answer 3

If you use the Developer Command Prompt for VS2012 (available under the Start Menu -> Programs -> Microsoft Visual Studio 2012 -> Visual Studio Tools), you'll have fsi (F# Interactive) in the path already. For example:

C:\Program Files (x86)\Microsoft Visual Studio 11.0>fsi

Microsoft (R) F# Interactive version 11.0.60315.1
Copyright (c) Microsoft Corporation. All Rights Reserved.

For help type #help;;

> #quit;;

C:\Program Files (x86)\Microsoft Visual Studio 11.0>

You can create F# script files -- they use the *.fsx file extension -- and then run them using fsi. Under Mono on OSX, FreeBSD, and Linux, you can also add a "shebang" to *.fsx files and run them just like you would a Python, Perl, etc. script.

EDIT: As far as running the external programs, there are some libraries on NuGet for simplifying this -- cmd is the first one I found. It's for C#, but it should be straightforward to implement some wrapper functions to make it easier to consume from F#.