File System

This package, filesystem, contains interfaces and structures for abstracting and wrapping file system interactions. Use this in lieu of the direct os and ioutil packages for manipulating files on a physical file system.

Interfaces

This package provides five interfaces which abstract a file system, a file object, and file reader/writer.

FileSystem

The interface FileSystem represents a system that reads and writes files and directories. It implements the following interfaces: fs.FS, fs.ReadFileFS, OpenFileFS, WriteFileFS, and DirWriterFS.

This means that any struct that implements FileSystem must provide the following methods:

• Mkdir(name string, perm fs.FileMode) error
• Open(name string) (fs.File, error)
• OpenFile(name string, flag int, perm os.FileMode) (WriteableFile, error)
• ReadFile(name string) ([]byte, error)
• Stat(name string) (fs.FileInfo, error)
• WriteFile(name string, data []byte, perm fs.FileMode) error

Use this interface when you need the full ability to read and write files.

DirWriterFS

DirWriterFS describes an interface to write directories in a file system. It provides the following:

• Mkdir(name string, perm fs.FileMode) error

OpenFileFS

OpenFileFS describes an interface to open a file and specify what kind of action you wish to perform on this file, such as reading, writing, and/or appending. This is similar to the Go fs.FS interface but adds the flag attribute.

• OpenFile(name string, flag int, perm os.FileMode) (WriteableFile, error)

WriteFileFS

WriteFileFS describes an interface to write bytes to a file system.

• WriteFile(name string, data []byte, perm fs.FileMode) error

WritableFile

WritableFile describes an interface to a file that can be both read and written to. This interface adds in fs.File for the reading interface, then adds additional methods for writing.

• Close() error
• Name() string
• Read(b []byte) (int, error)
• Stat() (fs.FileInfo, error)
• Write(b []byte) (int, error)
• WriteString(s string) (int, error)

Implementation

This package has the following packages that implement the interfaces described above.

• localfs
• memoryfs

localfs

localfs provides structs that implement the file system interfaces to work directly with a local OS file system. It implements the interface FileSystem.

package main

import (
	"fmt"

	"github.com/app-nerds/kit/v6/filesystem/localfs"
)

func main() {
	localFS := localfs.NewLocalFS()
	fileName := "test.txt"
	data := []byte("This is a text file!")

	if err := writeData(localFS, fileName, data); err != nil {
		panic("oh no!")
	}

	fmt.Printf("file written")
}

func writeData(fs filesystem.FileSystem, fileName string, data []byte) error {
	return fs.WriteFile(name, data, os.ModeAppend)
}

memoryfs

memoryfs provides structs that implement the file system interfaces to work with a file system that exists in memory. It implements the interface FileSystem.

package main

import (
	"fmt"

	"github.com/app-nerds/kit/v6/filesystem/memoryfs"
)

func main() {
	memoryFS := memoryfs.NewMemoryFS()
	fileName := "test.txt"
	data := []byte("This is a text file!")

	if err := writeData(localFS, fileName, data); err != nil {
		panic("oh no!")
	}

	fmt.Printf("file written")
}

func writeData(fs filesystem.FileSystem, fileName string, data []byte) error {
	return fs.WriteFile(name, data, os.ModeAppend)
}