# go-billy [](https://pkg.go.dev/github.com/go-git/go-billy/v5) [](https://github.com/go-git/go-billy/actions?query=workflow%3ATest)
The missing interface filesystem abstraction for Go.
Billy implements an interface based on the `os` standard library, allowing to develop applications without dependency on the underlying storage. Makes it virtually free to implement mocks and testing over filesystem operations.
Billy was born as part of [go-git/go-git ](https://github.com/go-git/go-git ) project.
## Installation
```go
import "github.com/go-git/go-billy/v5" // with go modules enabled (GO111MODULE=on or outside GOPATH)
import "github.com/go-git/go-billy" // with go modules disabled
```
## Usage
Billy exposes filesystems using the
[`Filesystem` interface ](https://pkg.go.dev/github.com/go-git/go-billy/v5?tab=doc#Filesystem ).
Each filesystem implementation gives you a `New` method, whose arguments depend on
the implementation itself, that returns a new `Filesystem` .
The following example caches in memory all readable files in a directory from any
billy's filesystem implementation.
```go
func LoadToMemory(origin billy.Filesystem, path string) (*memory.Memory, error) {
memory := memory.New()
files, err := origin.ReadDir("/")
if err != nil {
return nil, err
}
for _, file := range files {
if file.IsDir() {
continue
}
src, err := origin.Open(file.Name())
if err != nil {
return nil, err
}
dst, err := memory.Create(file.Name())
if err != nil {
return nil, err
}
if _, err = io.Copy(dst, src); err != nil {
return nil, err
}
if err := dst.Close(); err != nil {
return nil, err
}
if err := src.Close(); err != nil {
return nil, err
}
}
return memory, nil
}
```
## Why billy?
The library billy deals with storage systems and Billy is the name of a well-known, IKEA
bookcase. That's it.
## License
Apache License Version 2.0, see [LICENSE ](LICENSE )
