File I/O

The File struct represents a file that has been opened (it wraps a file descriptor), and gives read and/or write access to the underlying file.

Since many things can go wrong when doing file I/O, all the File methods return the io::Result<T> type, which is an alias for Result<T, io::Error>:

• This makes the failure of all I/O operations explicit.
• Thanks to this, the programmer can see all the failure paths, and is encouraged to handle them in a proactive manner.