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48 lines
1.7 KiB
Markdown
48 lines
1.7 KiB
Markdown
---
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title: replaceRE
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description: Returns a string, replacing all occurrences of a regular expression with a replacement pattern.
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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: [replace regex]
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signature:
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- "replaceRE PATTERN REPLACEMENT INPUT [LIMIT]"
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- "strings.ReplaceRE PATTERN REPLACEMENT INPUT [LIMIT]"
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relatedfuncs: [replace,findRE]
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aliases: []
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---
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By default, the `replaceRE` function replaces 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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The syntax of the regular expression is the same general syntax used by Perl, Python, and other languages. More precisely, it is the syntax accepted by [RE2] except for `\C`.
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This example replaces two or more consecutive hyphens with a single hyphen:
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```go-html-template
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{{ $s := "a-b--c---d" }}
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{{ replaceRE `(-{2,})` "-" $s }} → a-b-c-d
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```
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To limit the number of replacements to one:
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```go-html-template
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{{ $s := "a-b--c---d" }}
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{{ replaceRE `(-{2,})` "-" $s 1 }} → a-b-c---d
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```
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You can use `$1`, `$2`, etc. within the replacement string to insert the groups captured within the regular expression:
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```go-html-template
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{{ $s := "http://gohugo.io/docs" }}
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{{ replaceRE "^https?://([^/]+).*" "$1" $s }} → gohugo.io
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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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[RE2]: https://github.com/google/re2/wiki/Syntax
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[string literal]: https://go.dev/ref/spec#String_literals
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