How to run an EXE file compiled from a F# source on the Mac Terminal? - command-line

Question

I have a hello world program in F#.
open System
[<EntryPoint>]
let main argv =
printfn "Hello World from F#!"
0 // return an integer exit code%
On an Mac OS, I can compile it with "fsharpc", which generates two files
FSharp.Core.dll hello.exe
The EXE file certainly looks strange on a Mac. But how can I execute it from the command line, without using a project structure (because it seems an overkill) like what is explained here: https://dotnet.microsoft.com/learn/languages/fsharp-hello-world-tutorial/create
Actually if I run "dotnet hello.exe", I get this error:
A fatal error was encountered. The library 'libhostpolicy.dylib'
required to execute the application was not found in
'/Users/zell/hello/'. Failed to run as a self-contained app. If this
should be a framework-dependent app, add the
/Users/zell/hello/hello.runtimeconfig.json file specifying the
appropriate framework.

Answer 1

You can create and build/run F# apps like so:
dotnet new console -lang F# -o SomeDirectory && cd SomeDirectory
dotnet run
Building it without running is:
dotnet build
You can see a reference for all commands here: https://learn.microsoft.com/en-us/dotnet/core/tools/dotnet
You appear to have Mono installed, which is where fsharpc comes from. I wouldn't recommend using that unless you are doing mobile development with Xamarin, which currently requires Mono.

Answer 2

By trial and error, I found to run my new .exe file, I needed a .runtimeconfig.json file in the same folder with same without-the-extension-name, i.e. hello.runtimeconfig.json:
{
"runtimeOptions": {
"tfm": "net5.0",
"framework": {
"name": "Microsoft.NETCore.App",
"version": "5.0.0"
}
}
}
Then dotnet hello.exe will work.