Execute shell command (grunt build) with FAKE (F# make) - f#

Question

I want to automate the build process of my project using FAKE which requires me to run a grunt task.
In particular, I want to create a target that runs the grunt build task in a subfolder of the solution folder. Due to my lack of F# knowledge, I was not able to pass multiple parameters to the static Exec method of the Shell class. https://fsharp.github.io/FAKE/apidocs/fake-processhelper-shell.html
This is what I have got so far:
Target "RunGrunt" (fun _ ->
let errorCode = Shell.Exec "grunt" "build" "\Frontend"
()
)
This fails with the following error message:
build.fsx(38,23): error FS0003: This value is not a function and cannot be applied
If I remove the last 2 parameters, it works, but fails to find grunt at runtime:
System.ComponentModel.Win32Exception (0x80004005): The system cannot find the file specified
at System.Diagnostics.Process.StartWithCreateProcess(ProcessStartInfo startInfo)
at System.Diagnostics.Process.Start()
at Fake.ProcessHelper.start(Process proc) in C:\code\fake\src\app\FakeLib\ProcessHelper.fs:line 22
at Fake.ProcessHelper.asyncShellExec#424-2.Invoke(Process _arg1) in C:\code\fake\src\app\FakeLib\ProcessHelper.fs:line 428
at Microsoft.FSharp.Control.AsyncBuilderImpl.callA#851.Invoke(AsyncParams`1 args)
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.FSharp.Control.AsyncBuilderImpl.commit[a](Result`1 res)
at Microsoft.FSharp.Control.CancellationTokenOps.RunSynchronously[a](CancellationToken token, FSharpAsync`1 computation, FSharpOption`1 timeout)
at Microsoft.FSharp.Control.FSharpAsync.RunSynchronously[T](FSharpAsync`1 computation, FSharpOption`1 timeout, FSharpOption`1 cancellationToken)
at FSI_0001.Build.clo#34-6.Invoke(Unit _arg5) in D:\Development\Repos\FMVEAv2\Fmvea2-frontend\build.fsx:line 36
at Fake.TargetHelper.runSingleTarget(TargetTemplate`1 target) in C:\code\fake\src\app\FakeLib\TargetHelper.fs:line 483
Grunt is included in the path variable. (it works if called from the command line)
My questions are:
How can I pass multiple parameters to the Shell.Exec method?
How to run grunt, without including the complete path to it?

Answer 1

Both problems are now solved.
John pointed out in a comment to use tuple style instead of curried form which results in the following code:
Shell.Exec( "grunt","build","\FrontEnd")
FAKE provides a method to find a file on the path. http://fsharp.github.io/FAKE/apidocs/fake-processhelper.html
The target definition therefore looks like this:
Target "RunGrunt" (fun _ ->
let grunt = tryFindFileOnPath if isUnix then "grunt" else "grunt.cmd"
let errorCode = match grunt with
| Some g -> Shell.Exec(g, "build", "FrontEnd")
| None -> -1
()
)
neftedollar made a good point in the comments about cross platform compatiblity: Using the EnvironmentHelper to determine the platform and search for the correct executable of grunt.