A quick and dirty F# Shell Script to filter a text file for all lines which match a certain string

FilterTextFile.fsx

(*
* Filter a specified file into a second file
* Onorio Catenacci
* 21 October 2011
*)
#r "System.dll"

open System.IO

//Remember:
//When running from the command line, the first argument that isn't the script name is 1
//When running from FSI window, the first argument that isn't the script name is 0
let main = function
   [| _ ; source_file ; target_file |] ->
      let t_strings =               
         File.ReadLines(source_file)
         |> let pred prefix (cl : string) = cl.StartsWith(prefix) in Seq.filter (pred "Unit Disposition")
      File.WriteAllLines(target_file,t_strings)
      0
   | _ ->
      eprintfn "Bad arguments"
      1

main fsi.CommandLineArgs;;