Mastering Go - Second Edition

Finding out how fmt.Println() really works

If you really want to grasp the usefulness of the syscall package, start by reading this subsection. The implementation of the fmt.Println() function, as found in https://golang.org/src/fmt/print.go, is as follows:

func Println(a ...interface{}) (n int, err error) { 
    return Fprintln(os.Stdout, a...) 
} 

This means that the fmt.Println() function calls fmt.Fprintln() to do its job. The implementation of fmt.Fprintln(), as found in the same file, is as follows:

func Fprintln(w io.Writer, a ...interface{}) (n int, err error) { 
    p := newPrinter() 
    p.doPrintln(a) 
    n, err = w.Write(p.buf) 
    p.free() 
    return 
} 

This means that the actual writing in fmt.Fprintln() is done by the Write() function of the io.Writer ...