How to remove '---' on top of a YAML file?

问题:

I am modifying a YAML file in Ruby. After I write back the modified YAML, I see a --- added on top of the file. How is this getting added and how do I get rid of it?

回答1:

YAML spec says:

YAML uses three dashes (“---”) to separate directives from document content. This also serves to signal the start of a document if no directives are present.

Example:

# Ranking of 1998 home runs
---
- Mark McGwire
- Sammy Sosa
- Ken Griffey

# Team ranking
---
- Chicago Cubs
- St Louis Cardinals

So if you have multiple documents per YAML file, you have to separate them by three dashes. If you only have one document, you can remove/omit it (I never had a problem with YAML in ruby if three-dashes was missing). The reason why it's added when you yamlify your object is that, I guess, the dumper is written "by the spec" and doesn't care to implement such "shortcuts" (omit three-dashes when it's only one document).