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hugo/docs/content/en/functions/fmt/Warnf.md

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---
title: fmt.Warnf
description: Log a WARNING from a template.
categories: []
keywords: []
action:
aliases: [warnf]
related:
- functions/fmt/Errorf
- functions/fmt/Erroridf
- functions/fmt/Warnidf
returnType: string
signatures: ['fmt.Warnf FORMAT [INPUT]']
aliases: [/functions/warnf]
---
{{% include "functions/fmt/_common/fmt-layout.md" %}}
The `warnf` function evaluates the format string, then prints the result to the WARNING log. Hugo prints each unique message once to avoid flooding the log with duplicate warnings.
```go-html-template
{{ warnf "The %q shortcode was unable to find %s. See %s" .Name $file .Position }}
```
Use the [`warnidf`] function to allow optional suppression of specific warnings.
To prevent suppression of duplicate messages when using `warnf` for debugging, make each message unique with the [`math.Counter`] function. For example:
```go-html-template
{{ range site.RegularPages }}
{{ .Section | warnf "%#[2]v [%[1]d]" math.Counter }}
{{ end }}
```
[`math.Counter`]: /functions/math/counter/
[`warnidf`]: /functions/fmt/warnidf/