package main
import (
"io"
"os"
)
func main() {
// open input file
fi, err := os.Open("input.txt")
if err != nil {
panic(err)
}
// close fi on exit and check for its returned error
defer func() {
if err := fi.Close(); err != nil {
panic(err)
}
}()
// open output file
fo, err := os.Create("output.txt")
if err != nil {
panic(err)
}
// close fo on exit and check for its returned error
defer func() {
if err := fo.Close(); err != nil {
panic(err)
}
}()
// make a buffer to keep chunks that are read
buf := make([]byte, 1024)
for {
// read a chunk
n, err := fi.Read(buf)
if err != nil && err != io.EOF {
panic(err)
}
if n == 0 {
break
}
// write a chunk
if _, err := fo.Write(buf[:n]); err != nil {
panic(err)
}
}
}
package main
import (
"bufio"
"io"
"os"
)
func main() {
// open input file
fi, err := os.Open("input.txt")
if err != nil {
panic(err)
}
// close fi on exit and check for its returned error
defer func() {
if err := fi.Close(); err != nil {
panic(err)
}
}()
// make a read buffer
r := bufio.NewReader(fi)
// open output file
fo, err := os.Create("output.txt")
if err != nil {
panic(err)
}
// close fo on exit and check for its returned error
defer func() {
if err := fo.Close(); err != nil {
panic(err)
}
}()
// make a write buffer
w := bufio.NewWriter(fo)
// make a buffer to keep chunks that are read
buf := make([]byte, 1024)
for {
// read a chunk
n, err := r.Read(buf)
if err != nil && err != io.EOF {
panic(err)
}
if n == 0 {
break
}
// write a chunk
if _, err := w.Write(buf[:n]); err != nil {
panic(err)
}
}
if err = w.Flush(); err != nil {
panic(err)
}
}
package main
import (
"io/ioutil"
)
func main() {
// read the whole file at once
b, err := ioutil.ReadFile("input.txt")
if err != nil {
panic(err)
}
// write the whole body at once
err = ioutil.WriteFile("output.txt", b, 0644)
if err != nil {
panic(err)
}
}
package main
import (
"io"
"log"
"os"
)
func main () {
// open files r and w
r, err := os.Open("input.txt")
if err != nil {
panic(err)
}
defer r.Close()
w, err := os.Create("output.txt")
if err != nil {
panic(err)
}
defer w.Close()
// do the actual work
n, err := io.Copy(w, r)
if err != nil {
panic(err)
}
log.Printf("Copied %v bytes\n", n)
}
package main
import "os"
func main() {
b, err := os.ReadFile("input.txt")
if err != nil {
log.Fatal(err)
}
// `b` contains everything your file has.
// This writes it to the Standard Out.
os.Stdout.Write(b)
// You can also write it to a file as a whole.
err = os.WriteFile("destination.txt", b, 0644)
if err != nil {
log.Fatal(err)
}
}