hugo/docs/content/en/functions/findresubmatch.md

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findRESubmatch	Returns a slice of all successive matches of the regular expression. Each element is a slice of strings holding the text of the leftmost match of the regular expression and the matches, if any, of its subexpressions.	functions	docs parent functions	regex	findRESubmatch PATTERN INPUT [LIMIT] strings.FindRESubmatch PATTERN INPUT [LIMIT]	findRE replaceRE

By default, findRESubmatch finds all matches. You can limit the number of matches with an optional LIMIT parameter. A return value of nil indicates no match.

When specifying the regular expression, use a raw string literal (backticks) instead of an interpreted string literal (double quotes) to simplify the syntax. With an interpreted string literal you must escape backslashes.

This function uses the RE2 regular expression library. See the RE2 syntax documentation for details. Note that the RE2 \C escape sequence is not supported.

{{% note %}} The RE2 syntax is a subset of that accepted by PCRE, roughly speaking, and with various caveats.

{{% /note %}}

Demonstrative examples

{{ findRESubmatch `a(x*)b` "-ab-" }} → [["ab" ""]]
{{ findRESubmatch `a(x*)b` "-axxb-" }} → [["axxb" "xx"]]
{{ findRESubmatch `a(x*)b` "-ab-axb-" }} → [["ab" ""] ["axb" "x"]]
{{ findRESubmatch `a(x*)b` "-axxb-ab-" }} → [["axxb" "xx"] ["ab" ""]]
{{ findRESubmatch `a(x*)b` "-axxb-ab-" 1 }} → [["axxb" "xx"]]

Practical example

This markdown:

- [Example](https://example.org)
- [Hugo](https://gohugo.io)

Produces this HTML:

<ul>
  <li><a href="https://example.org">Example</a></li>
  <li><a href="https://gohugo.io">Hugo</a></li>
</ul>

To match the anchor elements, capturing the link destination and text:

{{ $regex := `<a\s*href="(.+?)">(.+?)</a>` }}
{{ $matches := findRESubmatch $regex .Content }}

Viewed as JSON, the data structure of $matches in the code above is:

[
  [
    "<a href=\"https://example.org\"></a>Example</a>",
    "https://example.org",
    "Example"
  ],
  [
    "<a href=\"https://gohugo.io\">Hugo</a>",
    "https://gohugo.io",
    "Hugo"
  ]
]

To render the href attributes:

{{ range $matches }}
  {{ index . 1 }}
{{ end }}

Result:

https://example.org
https://gohugo.io

{{% note %}} You can write and test your regular expression using regex101.com. Be sure to select the Go flavor before you begin. {{% /note %}}