57_writing_files.go

package gobyexample

import (
	"bufio"
	"fmt"
	"io/ioutil"
	"os"
)

// WriteFilesDemo - demonstrates writing files
func WriteFilesDemo() {
	// Here's how to dump a string (or just bytes) into a file.
	d1 := []byte("hello\ngo\n")
	err := ioutil.WriteFile("/tmp/dat1", d1, 0644)
	check(err)

	// For more granular writes, open a file for writing.
	f, err := os.Create("/tmp/dat2")
	check(err)

	// It is idiomatic to `defer` a `Close` immediately after
	// opening a file.
	defer f.Close()

	// You can write byte slices as you'd expect.
	d2 := []byte{115, 111, 109, 101, 10}
	n2, err := f.Write(d2)
	check(err)
	fmt.Printf("Wrote %d bytes\n", n2)

	// A `WriteString` is also available.
	n3, err := f.WriteString("writes\n")
	check(err)
	fmt.Printf("Wrote %d bytes\n", n3)

	// Issue a `Sync` to flush writes to stable storage.
	f.Sync()

	// `bufio` provides buffered writers in addition to the
	// buffered readers we saw earlier.
	w := bufio.NewWriter(f)
	n4, err := w.WriteString("buffered\n")
	check(err)
	fmt.Printf("Wrote %d bytes\n", n4)

	// Use `Flush` to ensure all buffered operations have been applied
	// to the underlying writer.
	w.Flush()
}