如何在Emacs中精确创建3位数字的regex?

{3} \b

\b[0-9]\{3\}\b

the docs

\bfoo\b foo \bballs?\b ball balls

(highlight-regexp "\\b[0-9]\\{3\\}\\b")

[0-9][0-9][0-9] [0-9]{3} \d{3}

^/[0-9]{3}/$ \w+[0-9]{3}\w+

(^|\D)\d{3}(\D|$)

"^\d{3}$"

ftp://ftp.newartisans.com/pub/emacs/regex-tool.el

[0-9][0-9][0-9]