This function reads a byte from the file without advancing to the next one. Successive calls to peek() will return the same value, as will the next call to read().
peek() inherits from the Stream utility class.
This communicates with the Linux distribution through Bridge. While functionally similar to the SD library, the underlying code and connections are different.
file: an instance of the File class (returned by FileIO.open())
The next byte (or character), or -1 if none is available.