In this article we will see two methods of copying a file.
Table of Contents
First Method
io.Copy() can be used to create a copy of the file from src to dest. A successful copy will return err != nil instead of err == EOF
Below is the signature of the function. It returns the number of bytes written to the dest
func Copy(dst Writer, src Reader) (written int64, err error)Code
First create a file named “original.txt” and write some content in it.
package main
import (
"fmt"
"io"
"log"
"os"
)
// Copy a file
func main() {
// Open original file
original, err := os.Open("original.txt")
if err != nil {
log.Fatal(err)
}
defer original.Close()
// Create new file
new, err := os.Create("new.txt")
if err != nil {
log.Fatal(err)
}
defer new.Close()
//This will copy
bytesWritten, err := io.Copy(new, original)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Bytes Written: %d\n", bytesWritten)
}Output:
Bytes Written: Second Method
If the contents of the file is less then we can also read the contents of the file first and then write all the contents to the new file. See below code.
Here also first create a file named “original.txt” and write some content in it
package main
import (
"io/ioutil"
"log"
)
// Copy a file
func main() {
//Read all the contents of the original file
bytesRead, err := ioutil.ReadFile("original.txt")
if err != nil {
log.Fatal(err)
}
//Copy all the contents to the desitination file
err = ioutil.WriteFile("new.txt", bytesRead, 0755)
if err != nil {
log.Fatal(err)
}
}Output
new.txt file will have same content as original.txt