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+---
+title: len
+linktitle: len
+description: Returns the length of a variable according to its type.
+godocref: https://golang.org/pkg/builtin/#len
+date: 2017-02-01
+publishdate: 2017-02-01
+lastmod: 2017-04-18
+categories: [functions]
+keywords: []
+signature: ["len INPUT"]
+workson: [lists,taxonomies,terms]
+hugoversion:
+relatedfuncs: []
+deprecated: false
+toc: false
+aliases: []
+---
+
+`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" >}}
+<header>
+    <h1{{if gt (len .Title) 80}} class="long-title"{{end}}>{{.Title}}</h1>
+</header>
+{{< /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][].
+
+
+[fundamental function for Hugo templating]: /templates/introduction/
+[list templates]: /templates/lists/
+[section]: /content-management/sections/
+[site variable]: /variables/site/
+[`where`]: /functions/where/