命令如 'stack exec — yesod --help'

Question

在Yesod书中 https://www.yesodweb.com/book/scaffolding-and-the-site-template 命令是这样给出的 'stack exec — yesod --help' 和 'stack exec — yesod devel' 但是那个'—'符号是什么（我只能复制/粘贴它），它是什么意思？

Answer 1

它被称为破折号 (and how to create it on your keyboard). In the case where it is being used with Yesod, it is somewhat unclear to me if using the em dash was on purpose or not. Some programs (like Microsoft Word) automatically convert two hyphens (--) into an em dash. I think this may be what happened in this case - because over at GitHub there is a post where the command stack exec -- yesod devel is used. This would be more consistent with typical command line usage of hyphens - the single and double hyphens are supposed to have specific/standard meaning when used in command line utilities。