What do backslashes in WP generated robots.txt rules mean?

Question

I am trying to implement a library to handle robots.txt and I am a bit confused about the meaning of some rules that I believe are generated by WordPress:

Disallow: /?s=*
Disallow: /*/?s=*\
Disallow: /\\?s=*

I have seen these rules on multiple WP sites.

I understand the first line, forbid entries with s parameter. But what do the other lines forbid? What is the meaning of the backslash characters in these lines?

Could someone give me an example or two for these 2 rules?

Answer 1

Backslashes in disallow rules are literals. Neither the original robots.txt specification, nor Google's extended interpretation treat / in any way specially.

My guess is that some WP plugin is adding those rules erroneously. Backslashes are not safe URL characters so they shouldn't appear as literals in URLs.