Neither ISO C nor POSIX offer functionality to determine the underlying OS during runtime. From a theoretical point of view, it doesn’t matter since C offers wrappers for the most common system calls, and from a nit-picking point of view, there doesn’t even have to be an underlying OS.
However, in many real-world scenarios, it has proven helpful to know more about the host environment than C is willing to share, e.g. in order to find out where to store config files or how to call select(), so:
Is there an idiomatic way for an application written in C to determine the underlying OS during runtime?
At least, can I easily decide between Linux, Windows, BSD and MacOS?
My current guess is to check for the existence of certain files/directories, such as C:\ or /, but this approach seems unreliable. Maybe querying a series of such sources may help to establish the notion of “OS fingerprints”, thus increasing reliability. Anyway, I’m looking forward to your suggestions.
Actually, most systems have a
unamecommand which shows the current kernel in use. On Mac OS, this is usually “Darwin”, on Linux it’s just plain “Linux”, on Windows it’s “ERROR” and FreeBSD will return “FreeBSD”.More complete list of
unameoutputsI’m pretty sure that there’s a C equivalent for
uname, so you won’t needsystem()