The methods of File parse their string value for a qualifier and look up a FileSystem in the Registry. The only special rule is, that if no qualifier is present, then the string value is interpreted as a local file path.

The LocalFileSystem is registered by default.

Work with Local directly:

fs.Local.Separator() // Either `/` or `\`

fs.Local.IsSymbolicLink("~/file") // Tilde expands to user home dir

For example, create a FileSystem from a multi-part HTTP form request that contains an uploaded file:

import "github.com/ungerik/go-fs/multipartfs"

multipartFS, err := multipartfs.FromRequestForm(request, MaxUploadSize)

defer multipartFS.Close()

// Access form values as string
multipartFS.Form.Value["email"] 

// Access form files as fs.File
file, err := multipartFS.FormFile("file")

// Use like any other fs.File
bytes, err := file.ReadAll(ctx)

fs.File

type File string

As a string-type it's easy to assign string literals and it can be const which would be impossible if File was an interface or struct:

const fileConst fs.File = "~/file.a"

var fileVar fs.File = "~/file.b"

fileVar = fileConst
fileVar = "~/file.c"

Handy to pass string literals of local paths or URIs to functions:

func readFile(f fs.File) { /* ... */ }

readFile("../my-local-file.txt")

// HTTP reading works when httpfs is imported
import _ "github.com/ungerik/go-fs/httpfs"

readFile("https://example.com/file-via-uri.txt")

As a string type File naturally marshals/unmarshals as string path/URI without having to implement marshaling interfaces.

But it implements fmt.Stringer to add the name of the path/URI filesystem as debug information and gob.GobEncoder, gob.GobDecoder to encode filename and content instead of the path/URI value.

Path related methods:

file := fs.TempDir().Join("file.txt")

dir := file.Dir()   // "/tmp" == fs.TempDir()
name := file.Name() // "file.txt"
path := file.Path() // "/tmp/file.txt"
url := file.URL()   // "file:///tmp/file.txt"
ext := file.Ext()   // ".txt"

file2 := file.Dir().Join("a", "b", "c").Joinf("file%d.txt", 2)
path2 := file2.Path() // "/tmp/a/b/c/file2.txt"

abs := fs.File("~/some-dir/../file").AbsPath() // "/home/erik/file"

Meta information:

size := file.Size() // int64, 0 for non existing or dirs
isDir := dir.IsDir()      // true
exists := file.Exists()   // true
fileIsDir := file.IsDir() // false
modTime := file.ModTime()
hash, err := file.ContentHash()  // Dropbox hash algo
regular := file.Info().IsRegular // true
info := file.Info().FSFileInfo() // io/fs.FileInfo

Reading and writing files

Reading:

bytes, err := file.ReadAll(ctx)

str, err := file.ReadAllString(ctx)

var w io.Writer
n, err := file.WriteTo(w)

f, err := file.OpenReader()     // io/fs.File 
r, err := file.OpenReadSeeker() // fs.ReadSeekCloser

Writing:

err := file.WriteAll(ctx, []byte("Hello"))

err := file.WriteAllString(ctx, "Hello")

err := file.Append(ctx, []byte("Hello"))

err := file.AppendString(ctx, "Hello")

var r io.Reader
n, err := file.ReadFrom(r)

w, err := file.OpenWriter()       // io.WriteCloser
w, err := file.OpenAppendWriter() // io.WriteCloser

rw, err := file.OpenReadWriter() // fs.ReadWriteSeekCloser

fs.FileReader

For cases where a file should be passed only for reading, it's recommended to use the interface type FileReader. It has all the read-related methods of File, so a File can be assigned or passed as FileReader:

type FileReader interface { /* ... */ }

func readFile(f fs.FileReader) { /* ... */ }

// An untyped string literal does not work as interface,
// needs a concrete type like fs.File
readFile(fs.File("../my-local-file.txt"))

fs.MemFile

MemFile combines the buffered in-memory data of a file with a filename to implement fs.FileReader. It exposes FileName and FileData as exported struct fields to emphasize its simple nature as just a wrapper of a name and some bytes.

type MemFile struct {
	FileName string
	FileData []byte
}

The type exists because it's very common to build up a file in memory and/or pass around some buffered file bytes together with a filename:

func readFile(f fs.FileReader) { /* ... */ }

readFile(fs.NewMemFile("hello-world.txt", []byte("Hello World!")))

// Read another fs.FileReader into a fs.MemFile
// to have it buffered in memory
memFile, err := fs.ReadMemFile(ctx, fs.File("../my-local-file.txt"))

// Read all data similar to io.ReadAll from an io.Reader
var r io.Rader
memFile, err := fs.ReadAllMemFile(cxt, r, "in-mem-file.txt")

Note that MemFile is not a File because it doesn't have a path or URI. The in-memory FileName is not interpreted as a path and should not contain path separators.

Listing directories

// Print names of all JPEGs in dir
dir.ListDir(func(f fs.File) error {
	_, err := fmt.Println(f.Name())
	return err
})

// Print names of all JPEGs in dir and all recursive sub-dirs
// with cancelable context
dir.ListDirRecursiveContext(ctx, func(f fs.File) error {
	_, err := fmt.Println(f.Name())
	return err
}, "*.jpg", "*.jpeg")

// Get all files in dir without limit
files, err := dir.ListDirMax(-1)

// Get the first 100 JPEGs in dir
files, err := dir.ListDirMaxContext(ctx, 100, "*.jpg", "*.jpeg")

Watching the local file system

TODO description

# Packages

# README

go-fs: A unified file system for Go