作者：Yihui Xie
译者：郑宝童
日期：2021.05.18

3 Output Formats

The bookdown package primarily supports three types of output formats: HTML, LaTeX/PDF, and e-books. In this chapter, we introduce the possible options for these formats. Output formats can be specified either in the YAML metadata of the first Rmd file of the book, or in a separate YAML file named _output.yml under the root directory of the book. Here is a brief example of the former (output formats are specified in the output field of the YAML metadata):

bookdown包主要支持三种输出格式:HTML、LaTeX/PDF和电子书。在本章中，我们将介绍这些格式的可能的选项。输出格式可以在书的第一个Rmd文件的YAML元数据中指定，也可以在书籍根目录下名为 _output.yml的单独YAML文件中指定。下面是前者的一个简单示例(输出格式在output的YAML元数据字段中指定): 

  1. ---
  2. title: "An Impressive Book"
  3. author: "Li Lei and Han Meimei"
  4. output:
  5.   bookdown::gitbook:
  6.     lib_dir: assets
  7.     split_by: section
  8.     config:
  9.       toolbar:
  10.         position: static
  11.   bookdown::pdf_book:
  12.     keep_tex: yes
  13.   bookdown::html_book:
  14.     css: toc.css
  15. documentclass: book
  16. ---

Here is an example of _output.yml:

这里展示一个 _output.yml的；例子:

  1. bookdown::gitbook:
  2.   lib_dir: assets
  3.   split_by: section
  4.   config:
  5.     toolbar:
  6.       position: static
  7. bookdown::pdf_book:
  8.   keep_tex: yes
  9. bookdown::html_book:
  10.   css: toc.css

In this case, all formats should be at the top level, instead of under an output field. You do not need the three dashes --- in _output.yml.
在这种情况下，所有格式都应该在顶层，而不是在output 字段下。您不需要在_output.yml.中使用三个破折号 --- 。