How to perform file system scanning

Here is an example to loop through all files and directories recursively. Note that if you want to know whether the path you're appending is a directory just check "f.IsDir()".

package main

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

func main() {
    searchDir := "c:/path/to/dir"

    fileList := []string{}
    err := filepath.Walk(searchDir, func(path string, f os.FileInfo, err error) error {
        fileList = append(fileList, path)
        return nil
    })

    for _, file := range fileList {
        fmt.Println(file)
    }
}

Package github.com/kr/fs provides a Walker with a very interesting API.

EDIT FOR 1.16: Enough people still hit this answer, that I thought I'd update it for Go 1.16.

The function filepath.WalkDir introduced in Go 1.16 has better performance than filepath.Walk mentioned in the previous edit. Here's a working example:

package main

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

func visit(path string, di fs.DirEntry, err error) error {
    fmt.Printf("Visited: %s\n", path)
    return nil
}

func main() {
    flag.Parse()
    root := flag.Arg(0)
    err := filepath.WalkDir(root, visit)
    fmt.Printf("filepath.WalkDir() returned %v\n", err)
}

EDIT: Enough people still hit this answer, that I thought I'd update it for the Go1 API. This is a working example of filepath.Walk(). The original is below.

package main

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

func visit(path string, f os.FileInfo, err error) error {
  fmt.Printf("Visited: %s\n", path)
  return nil
} 


func main() {
  flag.Parse()
  root := flag.Arg(0)
  err := filepath.Walk(root, visit)
  fmt.Printf("filepath.Walk() returned %v\n", err)
}

Please note that filepath.Walk walks the directory tree recursively.

This is an example run:

$ mkdir -p dir1/dir2
$ touch dir1/file1 dir1/dir2/file2
$ go run walk.go dir1
Visited: dir1
Visited: dir1/dir2
Visited: dir1/dir2/file2
Visited: dir1/file1
filepath.Walk() returned <nil>

ORIGINAL ANSWER FOLLOWS: The interface for walking file paths has changed as of weekly.2011-09-16, see http://groups.google.com/group/golang-nuts/msg/e304dd9cf196a218. The code below will not work for release versions of GO in the near future.

There's actually a function in the standard lib just for this: filepath.Walk.

package main

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

type visitor int

// THIS CODE NO LONGER WORKS, PLEASE SEE ABOVE
func (v visitor) VisitDir(path string, f *os.FileInfo) bool {
    println(path)
    return true
} 

func (v visitor) VisitFile(path string, f *os.FileInfo) {
    println(path)
}

func main() {
    root := flag.Arg(0)
    filepath.Walk(root, visitor(0), nil)
}

Here's a way to obtain file information for the files in a directory.

package main

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

func main() {
    dirname := "." + string(filepath.Separator)
    d, err := os.Open(dirname)
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
    defer d.Close()
    fi, err := d.Readdir(-1)
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
    for _, fi := range fi {
        if fi.Mode().IsRegular() {
            fmt.Println(fi.Name(), fi.Size(), "bytes")
        }
    }
}