Directories

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
}

$ 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