# Basic [File Manipulation] With Elixir

 
 

%[https://www.youtube.com/watch?v=w2ORd4nPCCc]

 
 


Learn how to do basic directories and files creation, open, read, write to files with Elixir.

### Step 1:

Let's create a new Elixir project by going to the command line and typing the following in your desired directory:

`$ mix new file_manipulator && cd file_manipulator`

### Step 2:

Open your test file `test/file_manipulator_test.exs`, remove the autogenerated test and add the following test:


```elixir
  setup do
    file = %{
      name: "test.exs",
      directory: "my_test",
      content: "IO.puts ",
      content_to_append: "\"Hello world from Elixir\""
    }

    %{my_file: file}
  end

  test "creates file", %{my_file: file} do
    my_file = FileManipulator.create(file)

    File.rm_rf!(file.directory)

    assert my_file == {:ok, :ok}
  end

  test "error when files exists", %{my_file: file} do
    FileManipulator.create(file)

    assert FileManipulator.create(file) == {:error, :eexist}

    File.rm_rf!(file.directory)
  end
```

Go to the command line and run the test `mix test` and see it fail.

### Step 3:

Let's make our test pass by opening our main project file `lib/file_manipulator.ex`, remove the autogenerated hello world function and add the following:

```elixir
  def create(file) do
    with :ok <- File.mkdir(file.directory),
         :ok <- File.write("#{file.directory}/#{file.name}", file.content)
    do
      append_to_file(file)
    else
      error ->
        error
    end
  end

  def append_to_file(my_file) do
    File.open("#{my_file.directory}/#{my_file.name}", [:read, :write], fn file ->
      IO.read(file, :line)
      IO.binwrite(file, my_file.content_to_append)
    end)
  end
```

Get back to the command line and run the test `mix test` now our test should pass with no failures.

### Code Breakdown

#### File.mkdir(path)

Makes the directory path if it doesn't exist, returns `:ok` if successful.

#### File.write(path, content)

Writes Content to the file path, creates the file if it doesn't exist, returns `:ok` if successful.

#### File.open(path, modes, function)

Opens the file in reading and writing mode.

#### IO.read(file, content)

Reads the content of the file, if you don't it gets overridden by the write function.

#### IO.binwrite(file, content)

Appends the content to the file.

## Conclusion

That's a simple introduction to file manipulation with Elixir, all you need is the `File`, and the input-output `IO` modules. Thank you so much for your time, I really appreciate it.


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