Copy a folder in go - go

Question

Is there an easy way to copy a directory in go?
I have the following function:
err = CopyDir("sourceFolder","destinationFolder")
Nothing so far has worked, including libraries such as github.com/cf-guardian/guardian/kernel/fileutils
One important thing to note is that I need to preserve directory structure, including the sourceFolder itself, not simply copy all contents of the folder.

Answer 1

I believe that docker implementation can be considered as complete solution for handling edge cases:
https://github.com/moby/moby/blob/master/daemon/graphdriver/copy/copy.go
There are following good things:
unsupported file type rise error
preserving permissions and ownership
preserving extended attributes
preserving timestamp
but because of a lot of imports your tiny application becomes huge.
I've tried to combine several solutions but use stdlib and for Linux only:
func CopyDirectory(scrDir, dest string) error {
entries, err := os.ReadDir(scrDir)
if err != nil {
return err
}
for _, entry := range entries {
sourcePath := filepath.Join(scrDir, entry.Name())
destPath := filepath.Join(dest, entry.Name())
fileInfo, err := os.Stat(sourcePath)
if err != nil {
return err
}
stat, ok := fileInfo.Sys().(*syscall.Stat_t)
if !ok {
return fmt.Errorf("failed to get raw syscall.Stat_t data for '%s'", sourcePath)
}
switch fileInfo.Mode() & os.ModeType{
case os.ModeDir:
if err := CreateIfNotExists(destPath, 0755); err != nil {
return err
}
if err := CopyDirectory(sourcePath, destPath); err != nil {
return err
}
case os.ModeSymlink:
if err := CopySymLink(sourcePath, destPath); err != nil {
return err
}
default:
if err := Copy(sourcePath, destPath); err != nil {
return err
}
}
if err := os.Lchown(destPath, int(stat.Uid), int(stat.Gid)); err != nil {
return err
}
fInfo, err := entry.Info()
if err != nil {
return err
}
isSymlink := fInfo.Mode()&os.ModeSymlink != 0
if !isSymlink {
if err := os.Chmod(destPath, fInfo.Mode()); err != nil {
return err
}
}
}
return nil
}
func Copy(srcFile, dstFile string) error {
out, err := os.Create(dstFile)
if err != nil {
return err
}
defer out.Close()
in, err := os.Open(srcFile)
defer in.Close()
if err != nil {
return err
}
_, err = io.Copy(out, in)
if err != nil {
return err
}
return nil
}
func Exists(filePath string) bool {
if _, err := os.Stat(filePath); os.IsNotExist(err) {
return false
}
return true
}
func CreateIfNotExists(dir string, perm os.FileMode) error {
if Exists(dir) {
return nil
}
if err := os.MkdirAll(dir, perm); err != nil {
return fmt.Errorf("failed to create directory: '%s', error: '%s'", dir, err.Error())
}
return nil
}
func CopySymLink(source, dest string) error {
link, err := os.Readlink(source)
if err != nil {
return err
}
return os.Symlink(link, dest)
}

Answer 2

This package seems to do exactly what you want to do, give it a try.
From the readme:
err := Copy("your/source/directory", "your/destination/directory")

Answer 3

Not satisfied with the already listed options which include using sketchy libraries, or vastly bloated libraries.
In my case, I opted to do things the old fashioned way. With shell commands!
import (
"os/exec"
)
func main() {
// completely arbitrary paths
oldDir := "/home/arshbot/"
newDir := "/tmp/"
cmd := exec.Command("cp", "--recursive", oldDir, newDir)
cmd.Run()
}

Answer 4

This solution copies a directory recursively, including symbolic links. Trying to be efficient in the actual copy stage using streams.
Also it's fairly easy to handle more of irregular files if needed.
// CopyDir copies the content of src to dst. src should be a full path.
func CopyDir(dst, src string) error {
return filepath.Walk(src, func(path string, info fs.FileInfo, err error) error {
if err != nil {
return err
}
// copy to this path
outpath := filepath.Join(dst, strings.TrimPrefix(path, src))
if info.IsDir() {
os.MkdirAll(outpath, info.Mode())
return nil // means recursive
}
// handle irregular files
if !info.Mode().IsRegular() {
switch info.Mode().Type() & os.ModeType {
case os.ModeSymlink:
link, err := os.Readlink(path)
if err != nil {
return err
}
return os.Symlink(link, outpath)
}
return nil
}
// copy contents of regular file efficiently
// open input
in, _ := os.Open(path)
if err != nil {
return err
}
defer in.Close()
// create output
fh, err := os.Create(outpath)
if err != nil {
return err
}
defer fh.Close()
// make it the same
fh.Chmod(info.Mode())
// copy content
_, err = io.Copy(fh, in)
return err
})
}

Answer 5

I've come up with a relatively shorter answer which uses path/filepath's Walk method:
import (
"io/ioutil"
"path/filepath"
"os"
"strings"
)
func copy(source, destination string) error {
var err error = filepath.Walk(source, func(path string, info os.FileInfo, err error) error {
var relPath string = strings.Replace(path, source, "", 1)
if relPath == "" {
return nil
}
if info.IsDir() {
return os.Mkdir(filepath.Join(destination, relPath), 0755)
} else {
var data, err1 = ioutil.ReadFile(filepath.Join(source, relPath))
if err1 != nil {
return err1
}
return ioutil.WriteFile(filepath.Join(destination, relPath), data, 0777)
}
})
return err
}

Answer 6

Also this might be a solution:
available on github.com/floscodes/golang-tools
import (
"fmt"
"io/ioutil"
"os"
)
func CopyDir(src string, dest string) error {
if dest[:len(src)] == src {
return fmt.Errorf("Cannot copy a folder into the folder itself!")
}
f, err := os.Open(src)
if err != nil {
return err
}
file, err := f.Stat()
if err != nil {
return err
}
if !file.IsDir() {
return fmt.Errorf("Source " + file.Name() + " is not a directory!")
}
err = os.Mkdir(dest, 0755)
if err != nil {
return err
}
files, err := ioutil.ReadDir(src)
if err != nil {
return err
}
for _, f := range files {
if f.IsDir() {
err = CopyDir(src+"/"+f.Name(), dest+"/"+f.Name())
if err != nil {
return err
}
}
if !f.IsDir() {
content, err := ioutil.ReadFile(src + "/" + f.Name())
if err != nil {
return err
}
err = ioutil.WriteFile(dest+"/"+f.Name(), content, 0755)
if err != nil {
return err
}
}
}
return nil
}