Go by Example: Directories and Paths

Go 1.23

Learn to manipulate the filesystem with Go's `os` and `path/filepath` packages. This example covers creating directories, reading directory contents, checking file existence, and recursively walking directory trees.

Code

package main

import (
    "fmt"
    "os"
    "path/filepath"
)

func check(e error) {
    if e != nil {
        panic(e)
    }
}

func main() {
    // Create a new directory
    err := os.Mkdir("subdir", 0755)
    check(err)

    // Defer cleanup
    defer os.RemoveAll("subdir")

    // Create a helper function to create empty files
    createEmptyFile := func(name string) {
        d := []byte("")
        check(os.WriteFile(name, d, 0644))
    }

    createEmptyFile("subdir/file1")

    // Create hierarchy of directories
    err = os.MkdirAll("subdir/parent/child", 0755)
    check(err)

    createEmptyFile("subdir/parent/file2")
    createEmptyFile("subdir/parent/file3")
    createEmptyFile("subdir/parent/child/file4")

    // Read directory contents
    c, err := os.ReadDir("subdir/parent")
    check(err)

    fmt.Println("Listing subdir/parent:")
    for _, entry := range c {
        fmt.Println(" ", entry.Name(), entry.IsDir())
    }

    // Change current working directory
    err = os.Chdir("subdir/parent/child")
    check(err)

    // Get current directory
    dir, err := os.Getwd()
    check(err)
    fmt.Println("CWD:", dir)

    // Walk directory tree recursively
    fmt.Println("Visiting subdir:")
    err = filepath.Walk("../../", visit)
}

// visit function called for every file/dir visited
func visit(path string, info os.FileInfo, err error) error {
    if err != nil {
        return err
    }
    fmt.Println(" ", path, info.IsDir())
    return nil
}

Explanation

Go provides distinct packages for filesystem operations: os for interacting with the operating system (creating, deleting, stating files) and path/filepath for manipulating path strings in a cross-platform way.

Key directory operations include:

Creating: os.MkdirAll(path, perm) is usually preferred over Mkdir as it creates parent directories as needed (like mkdir -p).
Reading: Use os.ReadDir (introduced in Go 1.16). It returns fs.DirEntry objects which are more efficient than the older os.FileInfo because they avoid unnecessary system calls (stat) for file details.
Walking: Use filepath.WalkDir (Go 1.16+) instead of filepath.Walk. It is significantly more performant for large directory trees because it streams directory entries and avoids stating every file unless requested.

Code Breakdown

17

Mkdir creates a new directory with the specified permissions (0755 = rwxr-xr-x).

32

MkdirAll creates a directory and all necessary parents. If the directory already exists, it does nothing (no error).

40

ReadDir reads the named directory and returns a list of directory entries sorted by filename.

59

filepath.Walk walks the file tree rooted at root, calling walkFn for each file or directory in the tree, including root.

Samplebadu

Go by Example: Directories and Paths

Code

Explanation

Code Breakdown