## 4.4 Configuration

We have mentioned rmd_files in Section 1.3, and there are more (optional) settings you can configure for a book in _bookdown.yml:

• book_filename: the filename of the main Rmd file, i.e., the Rmd file that is merged from all chapters; by default, it is named _main.Rmd.
• delete_merged_file: whether to delete the main Rmd file after the book is successfully rendered.
• before_chapter_script: one or multiple R scripts to be executed before each chapter, e.g., you may want to clear the workspace before compiling each chapter, in which case you can use rm(list = ls(all = TRUE)) in the R script.
• after_chapter_script: similar to before_chapter_script, and the R script is executed after each chapter.
• edit: a link that collaborators can click to edit the Rmd source document of the current page; this was designed primarily for GitHub repositories, since it is easy to edit arbitrary plain-text files on GitHub even in other people’s repositories (if you do not have write access to the repository, GitHub will automatically fork it and let you submit a pull request after you finish editing the file). This link should have %s in it, which will be substituted by the actual Rmd filename for each page.
• history: similar to edit, a link to the edit/commit history of the current page.
• view: similar to edit, a link to source code of the current page.
• rmd_subdir: whether to search for book source Rmd files in subdirectories (by default, only the root directory is searched). This may be either a boolean (e.g. true will search for book source Rmd files in the project directory and all subdirectories) or list of paths if you want to search for book source Rmd files in a subset of subdirectories.
• output_dir: the output directory of the book (_book by default); this setting is read and used by render_book().
• clean: a vector of files and directories to be cleaned by the clean_book() function.

Here is a sample _bookdown.yml:

book_filename: "my-book.Rmd"
delete_merged_file: true
before_chapter_script: ["script1.R", "script2.R"]
after_chapter_script: "script3.R"
view: https://github.com/rstudio/bookdown-demo/blob/master/%s
edit: https://github.com/rstudio/bookdown-demo/edit/master/%s
output_dir: "book-output"
clean: ["my-book.bbl", "R-packages.bib"]