File I/O

We shall now discuss file I/O in Go, which includes the use of the io.Reader and io.Writer interfaces, buffered and unbuffered I/O, as well as the bufio package.

Note: The io/ioutil package is deprecated in Go version 1.16. Existing Go code that uses the functionality of io/ioutil will continue to work, but it is better to stop using that package.

The io.Reader and io.Writer interfaces

This lesson presents the definitions of the popular io.Reader and io.Writer interfaces because these two interfaces are the basis of file I/O in Go—the former allows us to read from a file whereas the latter allows us to write to a file.

Definition of the io.Reader interface

The definition of the io.Reader interface is the following:

This definition, which should be revisited when we want one of our data types to satisfy the io.Reader interface, tells us the following:

• The Reader interface requires the implementation of a single method

• The parameter of Read() is a byte slice

• The return values of Read() are an integer and an error ...