Working with Directories in Go

Introduction

In this lab, you will learn how to work with directories in Go. Go provides several useful functions for working with directories in the file system.

Skills Graph

Directories

Create a Go program that creates a new sub-directory in the current working directory, creates a hierarchy of directories, including parents, lists directory contents, changes the current working directory, and visits a directory recursively.

• Create a new sub-directory in the current working directory.
• When creating temporary directories, it's good practice to defer their removal. os.RemoveAll will delete a whole directory tree (similarly to rm -rf).
• Create a hierarchy of directories, including parents with MkdirAll. This is similar to the command-line mkdir -p.
• ReadDir lists directory contents, returning a slice of os.DirEntry objects.
• Chdir lets us change the current working directory, similarly to cd.
• Visit a directory recursively, including all its sub-directories. Walk accepts a callback function to handle every file or directory visited.

$ 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

There is the full code below:

// Go has several useful functions for working with
// *directories* in the file system.

package main

import (
	"fmt"
	"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(os.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.DirEntry` objects.
	c, err := os.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 = os.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
}

Summary

In this lab, you learned how to work with directories in Go. You learned how to create a new sub-directory, create a hierarchy of directories, list directory contents, change the current working directory, and visit a directory recursively.