Question

Is it possible in C/C++ to create my own custom stream of type FILE (stdio.h) that can be used with fputs() for example ?

Answer 1

If your “custom stream” isn’t something you can represent with a file descriptor or file handle, then you’re out of luck. The FILE type is implementation-defined, so there’s no standard way to associate other things with one.

If you can get a C file descriptor for whatever it is you’re trying to write to, then you can call fdopen on it to turn it into a FILE*. It’s not standard C or C++, but it’s provided by Posix. On Windows, it’s spelled _fdopen.

If you’re using Windows and you have a HANDLE, then you can use _open_osfhandle to associate a file descriptor with it, and then use _fdopen from there.

Are you really tied to fputs? If not, then replace it with use of a C++ IOStream. Then you can provide your own descendant of std::basic_streambuf, wrap it in a std::ostream, and use standard C++ I/O on it.