サンプルで学ぶ Go 言語：Directories

Go has several useful functions for working with directories in the file system.
	package main
	import ( "fmt" "io/ioutil" "os" "path/filepath" )
	func check(e error) { if e != nil { panic(e) } }
	func main() {
Create a new sub-directory in the current working directory.	err := os.Mkdir("subdir", 0755) check(err)
When creating temporary directories, it’s good practice to `defer` their removal. `os.RemoveAll` will delete a whole directory tree (similarly to `rm -rf`).	defer os.RemoveAll("subdir")
Helper function to create a new empty file.	createEmptyFile := func(name string) { d := []byte("") check(ioutil.WriteFile(name, d, 0644)) }
	createEmptyFile("subdir/file1")
We can create a hierarchy of directories, including parents with `MkdirAll`. This is similar to the command-line `mkdir -p`.	err = os.MkdirAll("subdir/parent/child", 0755) check(err)
	createEmptyFile("subdir/parent/file2") createEmptyFile("subdir/parent/file3") createEmptyFile("subdir/parent/child/file4")
`ReadDir` lists directory contents, returning a slice of `os.FileInfo` objects.	c, err := ioutil.ReadDir("subdir/parent") check(err)
	fmt.Println("Listing subdir/parent") for _, entry := range c { fmt.Println(" ", entry.Name(), entry.IsDir()) }
`Chdir` lets us change the current working directory, similarly to `cd`.	err = os.Chdir("subdir/parent/child") check(err)
Now we’ll see the contents of `subdir/parent/child` when listing the current directory.	c, err = ioutil.ReadDir(".") check(err)
	fmt.Println("Listing subdir/parent/child") for _, entry := range c { fmt.Println(" ", entry.Name(), entry.IsDir()) }
`cd` back to where we started.	err = os.Chdir("../../..") check(err)
We can also visit a directory recursively, including all its sub-directories. `Walk` accepts a callback function to handle every file or directory visited.	fmt.Println("Visiting subdir") err = filepath.Walk("subdir", visit) }
`visit` is called for every file or directory found recursively by `filepath.Walk`.	func visit(p string, info os.FileInfo, err error) error { if err != nil { return err } fmt.Println(" ", p, info.IsDir()) return nil }

$ go run directories.go
Listing subdir/parent
  child true
  file2 false
  file3 false
Listing subdir/parent/child
  file4 false
Visiting subdir
  subdir true
  subdir/file1 false
  subdir/parent true
  subdir/parent/child true
  subdir/parent/child/file4 false
  subdir/parent/file2 false
  subdir/parent/file3 false

次の例：Temporary Files and Directories