Running F# scripts in unix without proper file extensions results in strange behaviour

[eiriktsarpalis]

In any unix environment with F# 4.0 installed, running

echo '#!/usr/bin/env fsharpi\nprintfn "Hello, World!"' > hello
chmod +x hello
./hello

Results in the following behaviour:

[12:43] eirik@eudoxos: ~/devel> ./hello

F# Interactive for F# 4.0 (Open Source Edition)
Freely distributed under the Apache 2.0 Open Source License

For help type #help;;

[Loading /home/eirik/devel/hello]


error FS0226: The file extension of '/home/eirik/devel/hello' is not recognized. Source files must have extension .fs, .fsi, .fsx, .fsscript, .ml or .mli.
>

While the error message clearly states what the problem is here, I think there are a couple of issues to notice:

• It is common practice to omit file extensions in executables. Perhaps we should consider supporting this in the fsi context?
• An invalid file extension will cause fsi to run in interactive mode, which seems a bit bizarre. It actually took me a while to understand what was going on because of all the text that was being output.

[KevinRansom]

@eiriktsarpalis
Yes I agree, restricting the extensions of files in this way is incorrect.

[eiriktsarpalis]

@KevinRansom Do you think we should lift this restriction for fsi only or the compiler in general?

[dsyme]

@eiriktsarpalis Just for FSI, and probably only for one script. I think the extension matters too much for the compiler, c.f. fs v. fsi v. fsx, shich all have different rules.

[nodakai]

I tried installing an F# script to replace /usr/bin/sendmail (wanted to forward cron failure mails to webhooks) only to discover this restriction. i ended up installing a Bash wrapper which calls the .fsx script but I felt that was an unnecessary indirection.

I wouldn’t mind passing an extra argument like --extension fsx to dotnet fsi if that helps

[T-Gro]

If we speak of dotnet fsi only, the extension restriction could be lifted.
I will mark it as help wanted - if anyone is interested into contribution, feel free to reach out and discuss possibilities.