How do I find all files that have a certain extension in Go, regardless of depth?

Question

I have a directory structure that looks like this:

/root
  /folder_1
    file_name_1.md
  /folder_2
    file_name_2.md
  /folder_3
    file_name_3.md
  /folder_4
    /sub_folder_1
      file_name_4_1.md
    file_name_4.md

Is there a glob function that I could use to get an array containing the file path of the .md files?

For example:

[
  "/root/folder_1/file_name_1.md",
  "/root/folder_2/file_name_2.md",
  "/root/folder_3/file_name_3.md",
  "/root/folder_4/sub_folder_1/file_name_4_1.md",
  "/root/folder_4/file_name_4.md"
]

Thanks.

Answer 1

Starting with Go 1.16 (Feb 2021), you can use filepath.WalkDir for better performance:

package main

import (
   "io/fs"
   "path/filepath"
)

func find(root, ext string) []string {
   var a []string
   filepath.WalkDir(root, func(s string, d fs.DirEntry, e error) error {
      if e != nil { return e }
      if filepath.Ext(d.Name()) == ext {
         a = append(a, s)
      }
      return nil
   })
   return a
}

func main() {
   for _, s := range find("/root", ".md") {
      println(s)
   }
}

https://golang.org/pkg/path/filepath#WalkDir

Answer 2

The function below will recursively walk through a directory and return the paths to all files whose name matches the given pattern:

func WalkMatch(root, pattern string) ([]string, error) {
    var matches []string
    err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
        if err != nil {
            return err
        }
        if info.IsDir() {
            return nil
        }
        if matched, err := filepath.Match(pattern, filepath.Base(path)); err != nil {
            return err
        } else if matched {
            matches = append(matches, path)
        }
        return nil
    })
    if err != nil {
        return nil, err
    }
    return matches, nil
}

Usage:

files, err := WalkMatch("/root/", "*.md")