FScript

FScript (Fsharp Script) provides a convenient way to write scripts in F# as if you are writing a shell script. It is a cross-platform tool that can run on Windows, Linux, and macOS as long as you have .NET SDK 7.0 or above installed.

Basic Usage

FScript is a library that can be imported into your F# script file. All you need to do is to add the following line to the top of your script file:

#r "nuget: B2R2.FScript"

You can then write your script as if you are writing a shell script. For example, the following script will execute the ls -la command and print the output to the console:

#!/usr/bin/env -S dotnet fsi
#r "nuget: B2R2.FScript"

open B2R2.FScript

!"ls" ["-la"]
=| fun cmd ->
  cmd.ReadStdout ()
  |> printfn "%s"

Note that the bang operator ! is used to execute a command, and the command instance is passed with the =| operator so that you can print out the output. You can also pipe the output to another command using the => operator.

#!/usr/bin/env -S dotnet fsi
#r "nuget: B2R2.FScript"

open B2R2.FScript
open System

!"cat" ["README.md"]
=> !"tail" ["-n"; "1"]
=| fun cmd ->
  Console.WriteLine $"Exit: {cmd.ExitCode.Value}"
  Console.WriteLine $"Stdout:\n{cmd.ReadStdout ()}"
  Console.WriteLine $"Stderr:\n{cmd.ReadStderr ()}"

The above script will print out the last line of this README.md file. You can use the => operator to pipe the output of cat to tail and print out the output of tail to the console. Note also that you can get the exit code of the last command by accessing the ExitCode property of the command instance.

TaskQueue

FScript provides a way to run multiple commands in parallel. To do so, you first instantiates a TaskQueue instance and then add commands to the queue. It will automatically consume the commands and run them in parallel by maximizing the number of cores on your machine. For example, the following script will run sha1sum on all files in the current directory:

#!/usr/bin/env -S dotnet fsi
#r "nuget: B2R2.FScript"

open B2R2.FScript
open System
open System.IO

let queue = TaskQueue ()
Directory.EnumerateFiles (".", "*", SearchOption.AllDirectories)
|> Seq.iter (fun f -> queue.AddTask <| !"sha1sum" [f])
queue.Wait ()
queue.Outputs
|> Array.iter (fun log -> Console.Write $"{log.CmdLine} -> {log.OutLog}")