fdev_setup_stream(stream, put, get, rwflag)
This macro takes a user-supplied buffer stream, and sets it
up as a stream that is valid for stdio operations, similar to one that has been obtained
dynamically from fdevopen(). The buffer to setup must be of type FILE.
The arguments put and get are identical to
those that need to be passed to fdevopen().
The rwflag argument can take one of the values
_FDEV_SETUP_READ, _FDEV_SETUP_WRITE, or _FDEV_SETUP_RW, for read, write, or read/write
intent, respectively.
No assignments to the standard streams will be performed by fdev_setup_stream(). If standard streams are to be used, these need to be assigned by the user. See also under Running stdio without malloc().