go 51 lines · 7 steps

Walking a directory tree to find large files in Go

A single WalkDir traversal filters by extension and size while skipping noisy directories.

Explained by highlit
Intermediate filesystem recursion closures error-handling
1package fsutil
2 
3import (
4 "io/fs"
5 "os"
6 "path/filepath"
7 "strings"
8)
9 
10type Match struct {
11 Path string
12 Size int64
13}
14 
15func FindLargeFiles(root, ext string, minSize int64) ([]Match, error) {
16 var matches []Match
17 ext = strings.ToLower(ext)
18 
19 err := filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
20 if err != nil {
21 if os.IsPermission(err) {
22 return nil
23 }
24 return err
25 }
26 
27 if d.IsDir() {
28 name := d.Name()
29 if name == ".git" || name == "node_modules" || name == "vendor" {
30 return filepath.SkipDir
31 }
32 return nil
33 }
34 
35 if ext != "" && !strings.EqualFold(filepath.Ext(path), ext) {
36 return nil
37 }
38 
39 info, err := d.Info()
40 if err != nil {
41 return err
42 }
43 
44 if info.Size() >= minSize {
45 matches = append(matches, Match{Path: path, Size: info.Size()})
46 }
47 return nil
48 })
49 
50 return matches, err
51}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1filepath.WalkDir drives a recursive traversal through one callback you supply per entry.
  2. 2Returning sentinel values like filepath.SkipDir or nil steers the walk without unwinding the whole traversal.
  3. 3Closing over an accumulator slice lets the callback collect results across the entire tree.

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