Its Markdown output will be:

Then the text output block will be converted to HTML by Pandoc:

The attr.source and options have made it possible for us to specify maximum heights for individual code chunks. However, the syntax is a little clunky, and requires a better understanding of CSS and Pandoc’s Markdown syntax. Below we show an example of a custom output hook that works with a custom chunk option max.height, so you will only need to set the chunk option like max.height = "100px" instead of attr.output = 'style="max-height: 100px;"'. In this example, we only manipulate the argument, but not the x argument.

Figure shows the output. Note that in the last code chunk with the chunk option attr.output, the option will not be overridden by max.height because we respect existing attributes by combining them with the style attribute generated by :

FIGURE 12.1: An example of scrollable text output, with its height specified in the chunk option max.height.

You can use a similar trick in the source hook to limit the height of source code blocks.