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

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title	linktitle	description	date	publishdate	lastmod	categories	menu	keywords	signature	workson	hugoversion	relatedfuncs	deprecated	toc	aliases
len	len	Returns the length of a variable according to its type.	2017-02-01	2017-02-01	2017-04-18	functions	docs parent functions		len INPUT	lists taxonomies terms			false	false

len is a built-in function in Go that returns the length of a variable according to its type. From the Go documentation:

Array: the number of elements in v.

Pointer to array: the number of elements in *v (even if v is nil).

Slice, or map: the number of elements in v; if v is nil, len(v) is zero.

String: the number of bytes in v.

Channel: the number of elements queued (unread) in the channel buffer; if v is nil, len(v) is zero.

len is also considered a fundamental function for Hugo templating.

len Example 1: Longer Headings

You may want to append a class to a heading according to the length of the string therein. The following templating checks to see if the title's length is greater than 80 characters and, if so, adds a long-title class to the <h1>:

{{< code file="check-title-length.html" >}}

{{.Title}} {{< /code >}}

len Example 2: Counting Pages with where

The following templating uses where in conjunction with len to figure out the total number of content pages in a posts section:

{{< code file="how-many-posts.html" >}} {{ $posts := (where .Site.RegularPages "Section" "==" "posts") }} {{ $postCount := len $posts }} {{< /code >}}

Note the use of .RegularPages, a site variable that counts all regular content pages but not the _index.md pages used to add front matter and content to list templates.