template/book/exercises/002.md

Exercise 2: Add a new file to the table of contents

Let's continue by adding one additional step. Let's add a file to the table of contents! the _toc.yml contains a list of all the files to be shown in your book-website. Let's add a file which is not in the table of contents yet!

::::::{topic} Exercise objective Can you add the file named file_to_be_added_to_toc.md to the book website? ::::::

1. Go to the {octicon}code;1em Code - Book directory of your GitHub repository and find the location of file_to_be_added_to_toc.md
2. Go to the the file book/_toc.yml on your GitHub repository - {octicon}code;1em Code - Book - _toc.yml - {octicon}pencil;1em Edit this file
3. Add file_to_be_added_to_toc.md as a second subpage under some_content/overview.md. some_content/text_and_code.ipynb is the first subpage.

:class: tip, dropdown
Your `_toc.yml` should look like
```yaml
format: jb-book
root: intro.md

parts:
  - caption: Contents
    chapters:
    - file: some_content/overview.md
      sections:
      - file: some_content/text_and_code.ipynb
      - file: file_to_be_added_to_toc.md
    - file: exercises/exercises
      sections:
      - file: exercises/001.md
      - file: exercises/002.md
      - file: exercises/003.md
      - file: exercises/004.md
      - file: exercises/005.md
      - file: exercises/006.md
    - file: references.md
    - file: changelog.md
    - file: credits.md
```

4. Click Commit changes
5. Add a message and description of your change
6. Select Commit directly to the main branch (this adds your change your change to the default version instead of making a new one)
7. Click Commit changes
8. Go to {octicon}play;1em Actions - The most recent workflow run Update _toc.yml / the commit message of the commit you just made - Wait for it to finish - In the summary, click on the link of your book shown in the table Branches deployed and under Primary book at root (getting bored of waiting? There'll be exercising on doing this locally which prevents you from waiting)
9. Do you see your change? If you don't see it click CTRL+F5/Control+F5to refresh the page.

:class: note

Before moving on to the next exercise, make sure you understand the following:
- Are all files in the repository added to the website?
- What is the purpose of the `_toc.yml` file?
- What happens if a file is not listed in the `_toc.yml`?
- How can you verify that your changes to `_toc.yml` were successful?
- Does the structure of the `_toc.yml` file need to match the directory structure of the repository?