Do not use exit() on mobile platforms

[Tobisaninfo]

Hi,

I try to use your library on iOS but get some compiler errors. The exit() method cannot be used on mobile platforms. Therefore Xcode reports some compiler errors. To use it anyway, I added a preprocessor statement to switch between mobile platforms and macOS/Linux.

[dastrobu]

@Tobisaninfo thanks for taking the time to create this PR. I guess I wasn't expecting anyone to use this on a mobile target, since CLI apps are not very common there 😉. (Of course, if you have multiple targets, it makes sense).

May I suggest a slightly alternative approach. You could change the imports from

#if os(macOS)
import Darwin
#elseif os(Linux)
import Glibc
#endif

to

#if canImport(Darwin)
import Darwin
#elseif canImport(Glibc)
import Glibc
#endif

The reason for the compile error is that Darwin was not imported on iOS (although it is available). That you should not use exit(0) on iOS is a different story, but this is probably something that should not be handled by this library.

[Tobisaninfo]

Sure your are right, the market of CLI apps isn't that big 😀 Recently I was looking for a arg parse framework for my iOS project, because I have some launch args for dev and UI test purpose. So none of them are for production, but it makes my development life much easier.

Thanks your fast feedback. I will have a look on your annotations and fix this things.

[dastrobu]

Thanks

[dastrobu]

@Tobisaninfo enjoy version 1.5.4.

[Tobisaninfo]

Thanks for the fast reply and new version of the library 😊