diff --git a/file.go b/file.go
index d9be4cd..b13ca39 100644
--- a/file.go
+++ b/file.go
@@ -597,12 +597,15 @@ func (file File) ListDirRecursiveChan(cancel <-chan error, patterns ...string) (
 	return files, errs
 }
 
-func (file File) User() string {
+func (file File) User() (string, error) {
+	if file == "" {
+		return "", ErrEmptyPath
+	}
 	fileSystem, path := file.ParseRawURI()
 	if fs, ok := fileSystem.(UserFileSystem); ok {
 		return fs.User(path)
 	}
-	return ""
+	return "", NewErrUnsupported(fileSystem, "User")
 }
 
 func (file File) SetUser(user string) error {
@@ -616,12 +619,15 @@ func (file File) SetUser(user string) error {
 	return NewErrUnsupported(fileSystem, "SetUser")
 }
 
-func (file File) Group() string {
+func (file File) Group() (string, error) {
+	if file == "" {
+		return "", ErrEmptyPath
+	}
 	fileSystem, path := file.ParseRawURI()
 	if fs, ok := fileSystem.(GroupFileSystem); ok {
 		return fs.Group(path)
 	}
-	return ""
+	return "", NewErrUnsupported(fileSystem, "Group")
 }
 
 func (file File) SetGroup(group string) error {
diff --git a/filesystem.go b/filesystem.go
index 63a131c..8f20273 100644
--- a/filesystem.go
+++ b/filesystem.go
@@ -235,14 +235,14 @@ type ExistsFileSystem interface {
 type UserFileSystem interface {
 	FileSystem
 
-	User(filePath string) string
+	User(filePath string) (string, error)
 	SetUser(filePath string, user string) error
 }
 
 type GroupFileSystem interface {
 	FileSystem
 
-	Group(filePath string) string
+	Group(filePath string) (string, error)
 	SetGroup(filePath string, group string) error
 }
 
diff --git a/httpfs/httpfs.go b/httpfs/httpfs.go
index 146b0df..1aa7cb2 100644
--- a/httpfs/httpfs.go
+++ b/httpfs/httpfs.go
@@ -171,14 +171,6 @@ func (f *HTTPFileSystem) ListDirInfo(ctx context.Context, dirPath string, callba
 	return fs.NewErrUnsupported(f, "ListDirInfo")
 }
 
-func (f *HTTPFileSystem) ListDirInfoRecursive(ctx context.Context, dirPath string, callback func(*fs.FileInfo) error, patterns []string) error {
-	return fs.NewErrUnsupported(f, "ListDirInfoRecursive")
-}
-
-func (f *HTTPFileSystem) ListDirMax(ctx context.Context, dirPath string, max int, patterns []string) ([]fs.File, error) {
-	return nil, fs.NewErrUnsupported(f, "ListDirMax")
-}
-
 func (f *HTTPFileSystem) ReadAll(ctx context.Context, filePath string) (data []byte, err error) {
 	if ctx.Err() != nil {
 		return nil, ctx.Err()
diff --git a/invalidfilesystem.go b/invalidfilesystem.go
index e833fdb..e457860 100644
--- a/invalidfilesystem.go
+++ b/invalidfilesystem.go
@@ -139,16 +139,16 @@ func (InvalidFileSystem) SetPermissions(filePath string, perm Permissions) error
 	return ErrInvalidFileSystem
 }
 
-func (InvalidFileSystem) User(filePath string) string {
-	return ""
+func (InvalidFileSystem) User(filePath string) (string, error) {
+	return "", ErrInvalidFileSystem
 }
 
 func (InvalidFileSystem) SetUser(filePath string, user string) error {
 	return ErrInvalidFileSystem
 }
 
-func (InvalidFileSystem) Group(filePath string) string {
-	return ""
+func (InvalidFileSystem) Group(filePath string) (string, error) {
+	return "", ErrInvalidFileSystem
 }
 
 func (InvalidFileSystem) SetGroup(filePath string, group string) error {
diff --git a/listdir_test.go b/listdir_test.go
index 4818d1e..4ce7cff 100644
--- a/listdir_test.go
+++ b/listdir_test.go
@@ -7,7 +7,7 @@ import (
 )
 
 func Test_listDirMaxImpl(t *testing.T) {
-	bg := context.Background()
+	ctx := context.Background()
 	errCtx, cancel := context.WithCancel(context.Background())
 	cancel()
 
@@ -37,11 +37,11 @@ func Test_listDirMaxImpl(t *testing.T) {
 		wantFiles []File
 		wantErr   bool
 	}{
-		{name: "-1", args: args{ctx: bg, max: -1, listDir: list("1", "2", "3")}, wantFiles: []File{"1", "2", "3"}},
-		{name: "-1 no files", args: args{ctx: bg, max: -1, listDir: list()}, wantFiles: nil},
-		{name: "0", args: args{ctx: bg, max: 0, listDir: list("1", "2", "3")}, wantFiles: nil},
-		{name: "1", args: args{ctx: bg, max: 1, listDir: list("1", "2", "3")}, wantFiles: []File{"1"}},
-		{name: "2", args: args{ctx: bg, max: 2, listDir: list("1", "2", "3")}, wantFiles: []File{"1", "2"}},
+		{name: "-1", args: args{ctx: ctx, max: -1, listDir: list("1", "2", "3")}, wantFiles: []File{"1", "2", "3"}},
+		{name: "-1 no files", args: args{ctx: ctx, max: -1, listDir: list()}, wantFiles: nil},
+		{name: "0", args: args{ctx: ctx, max: 0, listDir: list("1", "2", "3")}, wantFiles: nil},
+		{name: "1", args: args{ctx: ctx, max: 1, listDir: list("1", "2", "3")}, wantFiles: []File{"1"}},
+		{name: "2", args: args{ctx: ctx, max: 2, listDir: list("1", "2", "3")}, wantFiles: []File{"1", "2"}},
 
 		{name: "context error", args: args{ctx: errCtx, max: -1, listDir: list("1", "2", "3")}, wantErr: true},
 	}
diff --git a/localfilesystem.go b/localfilesystem.go
index 57c68d4..ddaa337 100644
--- a/localfilesystem.go
+++ b/localfilesystem.go
@@ -410,30 +410,6 @@ func (local *LocalFileSystem) SetPermissions(filePath string, perm Permissions)
 	return os.Chmod(filePath, mode)
 }
 
-func (local *LocalFileSystem) User(filePath string) string {
-	filePath = expandTilde(filePath)
-
-	panic("not implemented")
-}
-
-func (local *LocalFileSystem) SetUser(filePath string, user string) error {
-	filePath = expandTilde(filePath)
-
-	panic("not implemented")
-}
-
-func (local *LocalFileSystem) Group(filePath string) string {
-	filePath = expandTilde(filePath)
-
-	panic("not implemented")
-}
-
-func (local *LocalFileSystem) SetGroup(filePath string, group string) error {
-	filePath = expandTilde(filePath)
-
-	panic("not implemented")
-}
-
 func (local *LocalFileSystem) Touch(filePath string, perm []Permissions) error {
 	if filePath == "" {
 		return ErrEmptyPath
diff --git a/localfilesystem_unix.go b/localfilesystem_unix.go
index b111b7e..65311d3 100644
--- a/localfilesystem_unix.go
+++ b/localfilesystem_unix.go
@@ -1,7 +1,16 @@
+//go:build darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
 // +build darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package fs
 
+import (
+	"fmt"
+	"os"
+	"os/user"
+	"strconv"
+	"syscall"
+)
+
 const localRoot = `/`
 
 var extraDirPermissions Permissions = AllExecute
@@ -9,3 +18,81 @@ var extraDirPermissions Permissions = AllExecute
 func hasLocalFileAttributeHidden(path string) (bool, error) {
 	return false, nil
 }
+
+func (local *LocalFileSystem) User(filePath string) (string, error) {
+	if filePath == "" {
+		return "", ErrEmptyPath
+	}
+	filePath = expandTilde(filePath)
+
+	info, err := os.Stat(filePath)
+	if err != nil {
+		return "", err
+	}
+	stat, ok := info.Sys().(*syscall.Stat_t)
+	if !ok {
+		return "", NewErrUnsupported(local, "User")
+	}
+	u, err := user.LookupId(fmt.Sprint(stat.Uid))
+	if err != nil {
+		return "", err
+	}
+	return u.Username, nil
+}
+
+func (local *LocalFileSystem) SetUser(filePath string, username string) error {
+	if filePath == "" {
+		return ErrEmptyPath
+	}
+	filePath = expandTilde(filePath)
+
+	u, err := user.Lookup(username)
+	if err != nil {
+		return err
+	}
+	uid, err := strconv.Atoi(u.Uid)
+	if err != nil {
+		return err
+	}
+	return os.Chown(filePath, uid, -1)
+}
+
+func (local *LocalFileSystem) Group(filePath string) (string, error) {
+	if filePath == "" {
+		return "", ErrEmptyPath
+	}
+	filePath = expandTilde(filePath)
+
+	info, err := os.Stat(filePath)
+	if err != nil {
+		return "", err
+	}
+	stat, ok := info.Sys().(*syscall.Stat_t)
+	if !ok {
+		return "", NewErrUnsupported(local, "Group")
+	}
+	g, err := user.LookupGroupId(fmt.Sprint(stat.Gid))
+	if err != nil {
+		return "", err
+	}
+	return g.Name, nil
+}
+
+func (local *LocalFileSystem) SetGroup(filePath string, group string) error {
+	filePath = expandTilde(filePath)
+
+	if filePath == "" {
+		return ErrEmptyPath
+	}
+	filePath = expandTilde(filePath)
+
+	g, err := user.LookupGroup(group)
+	if err != nil {
+		return err
+	}
+	gid, err := strconv.Atoi(g.Gid)
+	if err != nil {
+		return err
+	}
+	return os.Chown(filePath, -1, gid)
+}
diff --git a/memfilesystem.go b/memfilesystem.go
index b63eb9b..78725a6 100644
--- a/memfilesystem.go
+++ b/memfilesystem.go
@@ -16,7 +16,7 @@ import (
 )
 
 var (
-	_ fullyFeaturedFileSystem = new(MemFileSystem)
+	_ FileSystem = new(MemFileSystem)
 
 	// memFileNode implements io/fs.FileInfo
 	_ iofs.FileInfo = new(memFileInfo)
@@ -217,8 +217,7 @@ func (fs *MemFileSystem) MakeAllDirs(dirPath string, perm []Permissions) error {
 	// }
 	// parentDir.Dir[pathParts[len(pathParts)-1]] = fs.newMemFileInfo(f, modified)
 
-	panic("todo")
-
+	panic("TODO")
 }
 
 func (fs *MemFileSystem) IsReadOnly() bool {
@@ -410,28 +409,20 @@ func (*MemFileSystem) ListDirInfo(ctx context.Context, dirPath string, callback
 	return nil
 }
 
-func (*MemFileSystem) ListDirInfoRecursive(ctx context.Context, dirPath string, callback func(*FileInfo) error, patterns []string) error {
-	return nil
-}
-
-func (*MemFileSystem) ListDirMax(ctx context.Context, dirPath string, n int, patterns []string) (files []File, err error) {
-	return nil, nil
-}
-
 func (*MemFileSystem) SetPermissions(filePath string, perm Permissions) error {
 	return nil
 }
 
-func (*MemFileSystem) User(filePath string) string {
-	return ""
+func (*MemFileSystem) User(filePath string) (string, error) {
+	return "", nil
 }
 
 func (*MemFileSystem) SetUser(filePath string, user string) error {
 	return nil
 }
 
-func (*MemFileSystem) Group(filePath string) string {
-	return ""
+func (*MemFileSystem) Group(filePath string) (string, error) {
+	return "", nil
 }
 
 func (*MemFileSystem) SetGroup(filePath string, group string) error {
diff --git a/readonlybase.go b/readonlybase.go
index 106a0ee..f95d077 100644
--- a/readonlybase.go
+++ b/readonlybase.go
@@ -29,14 +29,10 @@ func (*ReadOnlyBase) SetPermissions(filePath string, perm Permissions) error {
 	return ErrReadOnlyFileSystem
 }
 
-func (*ReadOnlyBase) User(filePath string) string { return "" }
-
 func (*ReadOnlyBase) SetUser(filePath string, user string) error {
 	return ErrReadOnlyFileSystem
 }
 
-func (*ReadOnlyBase) Group(filePath string) string { return "" }
-
 func (*ReadOnlyBase) SetGroup(filePath string, group string) error {
 	return ErrReadOnlyFileSystem
 }
diff --git a/subfilesystem.go b/subfilesystem.go
index e97cfe7..0aaab12 100644
--- a/subfilesystem.go
+++ b/subfilesystem.go
@@ -100,7 +100,7 @@ func (subfs *todoSubFileSystem) MatchAnyPattern(name string, patterns []string)
 }
 
 func (subfs *todoSubFileSystem) SplitDirAndName(filePath string) (dir, name string) {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) VolumeName(filePath string) string {
@@ -139,73 +139,73 @@ func (subfs *todoSubFileSystem) IsSymbolicLink(filePath string) bool {
 }
 
 func (subfs *todoSubFileSystem) ListDirInfo(ctx context.Context, dirPath string, callback func(*FileInfo) error, patterns []string) error {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) ListDirInfoRecursive(ctx context.Context, dirPath string, callback func(*FileInfo) error, patterns []string) error {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) ListDirMax(ctx context.Context, dirPath string, max int, patterns []string) (files []File, err error) {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) SetPermissions(filePath string, perm Permissions) error {
-	panic("not implemented")
+	panic("TODO")
 }
 
-func (subfs *todoSubFileSystem) User(filePath string) string {
-	panic("not implemented")
+func (subfs *todoSubFileSystem) User(filePath string) (string, error) {
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) SetUser(filePath string, user string) error {
-	panic("not implemented")
+	panic("TODO")
 }
 
-func (subfs *todoSubFileSystem) Group(filePath string) string {
-	panic("not implemented")
+func (subfs *todoSubFileSystem) Group(filePath string) (string, error) {
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) SetGroup(filePath string, group string) error {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) Touch(filePath string, perm []Permissions) error {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) MakeDir(filePath string, perm []Permissions) error {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) ReadAll(ctx context.Context, filePath string) ([]byte, error) {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) WriteAll(ctx context.Context, filePath string, data []byte, perm []Permissions) error {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) OpenReader(filePath string) (ReadCloser, error) {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) OpenWriter(filePath string, perm []Permissions) (WriteCloser, error) {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) OpenAppendWriter(filePath string, perm []Permissions) (WriteCloser, error) {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) OpenReadWriter(filePath string, perm []Permissions) (ReadWriteSeekCloser, error) {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) Truncate(filePath string, size int64) error {
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (subfs *todoSubFileSystem) Remove(filePath string) error {
-	panic("not implemented")
+	panic("TODO")
 }
diff --git a/zipfs/zipfs.go b/zipfs/zipfs.go
index 3f87fae..6f7da9d 100644
--- a/zipfs/zipfs.go
+++ b/zipfs/zipfs.go
@@ -244,7 +244,7 @@ func (zipfs *ZipFileSystem) ListDirInfo(ctx context.Context, dirPath string, cal
 		return fs.ErrWriteOnlyFileSystem
 	}
 
-	panic("not implemented")
+	panic("TODO")
 }
 
 func (zipfs *ZipFileSystem) ListDirInfoRecursive(ctx context.Context, dirPath string, callback func(*fs.FileInfo) error, patterns []string) error {