The du command is implemented.

du/.gitignore

@@ -0,0 +1,2 @@
+du
+du.exe

du/Makefile

@@ -0,0 +1,4 @@
+
+
+build:
+	go build .

du/go.mod

@@ -0,0 +1,3 @@
+module lcthw.dev/go/go-coreutils/du
+
+go 1.25.3

du/main.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+  "fmt"
+  "log"
+  "flag"
+  "io/fs"
+  "path/filepath"
+)
+
+func StatDir(target_path string) error {
+  var cur_dir string
+  var cur_size int64
+
+  // NOTE: cover the difference betweeen filepath.WalkDir and fs.WalkDir
+
+  err := filepath.WalkDir(target_path, func (path string, d fs.DirEntry, err error) error {
+    if d.IsDir() {
+      if cur_dir != path {
+        loc := filepath.Join(target_path, cur_dir)
+        fmt.Printf("%s %d\n", loc, cur_size / 1024)
+        cur_dir = path
+        cur_size = 0
+      }
+    } else {
+      info, err := d.Info()
+      if err != nil { return nil }
+      cur_size += info.Size()
+    }
+
+    return nil
+  })
+
+  return err
+}
+
+func main() {
+  flag.Parse()
+  paths := flag.Args()
+
+  for _, path := range paths {
+    err := StatDir(path)
+    if err != nil { log.Fatal(err) }
+  }
+}

stat/main.go

@@ -23,6 +23,7 @@ func main() {
   for _, fname := range files {
     f, err := os.Open(fname)
     if err != nil { log.Fatal(err) }
+    defer f.Close()
 
     stats, err := f.Stat()
     if err != nil { log.Fatal(err) }