memfs

README

memfs: A simple in-memory io/fs.FS filesystem

memfs is an in-memory implementation of Go's io/fs.FS interface. The goal is to make it easy and quick to build an fs.FS filesystem when you don't have any complex requirements.

Documentation: https://pkg.go.dev/github.com/psanford/memfs

io/fs docs: https://tip.golang.org/pkg/io/fs/

Usage

package main

import (
	"fmt"
	"io/fs"

	"github.com/psanford/memfs"
)

func main() {
	rootFS := memfs.New()

	err := rootFS.MkdirAll("dir1/dir2", 0777)
	if err != nil {
		panic(err)
	}

	err = rootFS.WriteFile("dir1/dir2/f1.txt", []byte("incinerating-unsubstantial"), 0755)
	if err != nil {
		panic(err)
	}

	err = fs.WalkDir(rootFS, ".", func(path string, d fs.DirEntry, err error) error {
		fmt.Println(path)
		return nil
	})
	if err != nil {
		panic(err)
	}

	content, err := fs.ReadFile(rootFS, "dir1/dir2/f1.txt")
	if err != nil {
		panic(err)
	}
	fmt.Printf("%s\n", content)
}

Documentation

Index

• type FS
  • func New(opts ...Option) *FS
  • func (rootFS *FS) MkdirAll(path string, perm os.FileMode) error
  • func (rootFS *FS) Open(name string) (fs.File, error)
  • func (rootFS *FS) Sub(path string) (fs.FS, error)
  • func (rootFS *FS) WriteFile(path string, data []byte, perm os.FileMode) error
• type File
  • func (f *File) Close() error
  • func (f *File) Read(b []byte) (int, error)
  • func (f *File) Seek(offset int64, whence int) (int64, error)
  • func (f *File) Stat() (fs.FileInfo, error)
• type Option
  • func WithOpenHook(f func(string, []byte, error) ([]byte, error)) Option

Examples

• New

Types

type FS

type FS struct {
	// contains filtered or unexported fields
}

FS is an in-memory filesystem that implements io/fs.FS

func New

func New(opts ...Option) *FS

New creates a new in-memory FileSystem.

Example

package main

import (
	"fmt"
	"io/fs"

	"github.com/psanford/memfs"
)

func main() {
	rootFS := memfs.New()

	err := rootFS.MkdirAll("dir1/dir2", 0777)
	if err != nil {
		panic(err)
	}

	err = rootFS.WriteFile("dir1/dir2/f1.txt", []byte("incinerating-unsubstantial"), 0755)
	if err != nil {
		panic(err)
	}

	err = fs.WalkDir(rootFS, ".", func(path string, d fs.DirEntry, err error) error {
		fmt.Println(path)
		return nil
	})
	if err != nil {
		panic(err)
	}

	content, err := fs.ReadFile(rootFS, "dir1/dir2/f1.txt")
	if err != nil {
		panic(err)
	}
	fmt.Printf("%s\n", content)
}

func (*FS) MkdirAll

func (rootFS *FS) MkdirAll(path string, perm os.FileMode) error

MkdirAll creates a directory named path, along with any necessary parents, and returns nil, or else returns an error. The permission bits perm (before umask) are used for all directories that MkdirAll creates. If path is already a directory, MkdirAll does nothing and returns nil.

func (*FS) Open

func (rootFS *FS) Open(name string) (fs.File, error)

Open opens the named file.

func (*FS) Sub

func (rootFS *FS) Sub(path string) (fs.FS, error)

Sub returns an FS corresponding to the subtree rooted at path.

func (*FS) WriteFile

func (rootFS *FS) WriteFile(path string, data []byte, perm os.FileMode) error

WriteFile writes data to a file named by filename. If the file does not exist, WriteFile creates it with permissions perm (before umask); otherwise WriteFile truncates it before writing, without changing permissions.

type File

type File struct {
	// contains filtered or unexported fields
}

func (*File) Close

func (f *File) Close() error

func (*File) Read

func (f *File) Read(b []byte) (int, error)

func (*File) Seek

func (f *File) Seek(offset int64, whence int) (int64, error)

func (*File) Stat

func (f *File) Stat() (fs.FileInfo, error)

type Option

type Option interface {
	// contains filtered or unexported methods
}

func WithOpenHook

func WithOpenHook(f func(string, []byte, error) ([]byte, error)) Option

WithOpenHook returns an Option that sets a hook function to be called when opening files in the MemFS.

The hook function takes three parameters:

• path: the path of the file being opened
• content: the original content of the file (may be nil if the file doesn't exist)
• origError: the original error returned when trying to open the file (may be nil)

The hook function returns:

• []byte: the new content of the file
• error: any error that occurred during the hook's execution