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49 lines
1.7 KiB
Markdown
49 lines
1.7 KiB
Markdown
---
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title: findRE
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description: Returns a slice of strings that match the regular expression.
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categories: [functions]
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menu:
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docs:
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parent: functions
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keywords: [regex]
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signature:
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- "findRE PATTERN INPUT [LIMIT]"
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- "strings.FindRE PATTERN INPUT [LIMIT]"
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relatedfuncs: [findRESubmatch, replaceRE]
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---
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By default, `findRE` finds all matches. You can limit the number of matches with an optional LIMIT parameter.
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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.
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[string literal]: https://go.dev/ref/spec#String_literals
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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.
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[RE2]: https://github.com/google/re2/
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[RE2 syntax documentation]: https://github.com/google/re2/wiki/Syntax/
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{{% note %}}
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The RE2 syntax is a subset of that accepted by [PCRE], roughly speaking, and with various [caveats].
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[caveats]: https://swtch.com/~rsc/regexp/regexp3.html#caveats
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[PCRE]: https://www.pcre.org/
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{{% /note %}}
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This example returns a slice of all second level headings (`h2` elements) within the rendered `.Content`:
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```go-html-template
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{{ findRE `(?s)<h2.*?>.*?</h2>` .Content }}
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```
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The `s` flag causes `.` to match `\n` as well, allowing us to find an `h2` element that contains newlines.
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To limit the number of matches to one:
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```go-html-template
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{{ findRE `(?s)<h2.*?>.*?</h2>` .Content 1 }}
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```
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{{% note %}}
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You can write and test your regular expression using [regex101.com](https://regex101.com/). Be sure to select the Go flavor before you begin.
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{{% /note %}}
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