Merge commit '9b0050e9aabe4be65c78ccf292a348f309d50ccd' as 'docs'

```
git subtree add --prefix=docs/ https://github.com/gohugoio/hugoDocs.git master --squash
```

Closes #11925

docs/content/en/functions/os/FileExists.md

@@ -0,0 +1,41 @@
+---
+title: os.FileExists
+description: Reports whether the file or directory exists.
+categories: []
+keywords: []
+action:
+  aliases: [fileExists]
+  related:
+    - functions/os/Getenv
+    - functions/os/ReadDir
+    - functions/os/ReadFile
+    - functions/os/Stat
+  returnType: bool
+  signatures: [os.FileExists PATH]
+aliases: [/functions/fileexists]
+---
+
+The `os.FileExists` function attempts to resolve the path relative to the root of your project directory. If a matching file or directory is not found, it will attempt to resolve the path relative to the [`contentDir`](/getting-started/configuration#contentdir). A leading path separator (`/`) is optional.
+
+With this directory structure:
+
+```text
+content/
+├── about.md
+├── contact.md
+└── news/
+    ├── article-1.md
+    └── article-2.md
+```
+
+The function returns these values:
+
+```go-html-template
+{{ fileExists "content" }} → true
+{{ fileExists "content/news" }} → true
+{{ fileExists "content/news/article-1" }} → false
+{{ fileExists "content/news/article-1.md" }} → true
+{{ fileExists "news" }} → true
+{{ fileExists "news/article-1" }} → false
+{{ fileExists "news/article-1.md" }} → true
+```

docs/content/en/functions/os/Getenv.md

@@ -0,0 +1,61 @@
+---
+title: os.Getenv
+description: Returns the value of an environment variable, or an empty string if the environment variable is not set.
+categories: []
+keywords: []
+action:
+  aliases: [getenv]
+  related:
+    - functions/os/FileExists
+    - functions/os/ReadDir
+    - functions/os/ReadFile
+    - functions/os/Stat
+  returnType: string
+  signatures: [os.Getenv VARIABLE]
+aliases: [/functions/getenv]
+toc: true
+---
+
+## Security
+
+By default, when using the `os.Getenv` function Hugo allows access to:
+
+- The `CI` environment variable
+- Any environment variable beginning with `HUGO_`
+
+To access other environment variables, adjust your site configuration. For example, to allow access to the `HOME` and `USER` environment variables:
+
+{{< code-toggle file=hugo >}}
+[security.funcs]
+getenv = ['^HUGO_', '^CI$', '^USER$', '^HOME$']
+{{< /code-toggle >}}
+
+Read more about Hugo's [security policy].
+
+[security policy]: /about/security-model/#security-policy
+
+## Examples
+
+```go-html-template
+{{ getenv "HOME" }} → /home/victor
+{{ getenv "USER" }} → victor
+```
+
+You can pass values when building your site:
+
+```sh
+MY_VAR1=foo MY_VAR2=bar hugo
+
+OR
+
+export MY_VAR1=foo
+export MY_VAR2=bar
+hugo
+```
+
+And then retrieve the values within a template:
+
+```go-html-template
+{{ getenv "MY_VAR1" }} → foo
+{{ getenv "MY_VAR2" }} → bar
+```

docs/content/en/functions/os/ReadDir.md

@@ -0,0 +1,51 @@
+---
+title: os.ReadDir
+description: Returns an array of FileInfo structures sorted by file name, one element for each directory entry.
+categories: []
+keywords: []
+action:
+  aliases: [readDir]
+  related:
+    - functions/os/FileExists
+    - functions/os/Getenv
+    - functions/os/ReadFile
+    - functions/os/Stat
+  returnType: os.FileInfo
+  signatures: [os.ReadDir PATH]
+aliases: [/functions/readdir]
+---
+
+The `os.ReadDir` function resolves the path relative to the root of your project directory. A leading path separator (`/`) is optional.
+
+With this directory structure:
+
+```text
+content/
+├── about.md
+├── contact.md
+└── news/
+    ├── article-1.md
+    └── article-2.md
+```
+
+This template code:
+
+```go-html-template
+{{ range readDir "content" }}
+  {{ .Name }} → {{ .IsDir }}
+{{ end }}
+```
+
+Produces:
+
+```html
+about.md → false
+contact.md → false
+news → true
+```
+
+Note that `os.ReadDir` is not recursive.
+
+Details of the `FileInfo` structure are available in the [Go documentation](https://pkg.go.dev/io/fs#FileInfo).
+
+For more information on using `readDir` and `readFile` in your templates, see [Local File Templates](/templates/files).

docs/content/en/functions/os/ReadFile.md

@@ -0,0 +1,40 @@
+---
+title: os.ReadFile
+description: Returns the contents of a file.
+categories: []
+keywords: []
+action:
+  aliases: [readFile]
+  related:
+    - functions/os/FileExists
+    - functions/os/Getenv
+    - functions/os/ReadDir
+    - functions/os/Stat
+  returnType: string
+  signatures: [os.ReadFile PATH]
+aliases: [/functions/readfile]
+---
+
+The `os.ReadFile` function attempts to resolve the path relative to the root of your project directory. If a matching file is not found, it will attempt to resolve the path relative to the [`contentDir`](/getting-started/configuration#contentdir). A leading path separator (`/`) is optional.
+
+With a file named README.md in the root of your project directory:
+
+```text
+This is **bold** text.
+```
+
+This template code:
+
+```go-html-template
+{{ readFile "README.md" }}
+```
+
+Produces:
+
+```html
+This is **bold** text.
+```
+
+Note that `os.ReadFile` returns raw (uninterpreted) content.
+
+For more information on using `readDir` and `readFile` in your templates, see [Local File Templates](/templates/files).

docs/content/en/functions/os/Stat.md

@@ -0,0 +1,31 @@
+---
+title: os.Stat
+description: Returns a FileInfo structure describing a file or directory.
+categories: []
+keywords: []
+action:
+  aliases: []
+  related:
+    - functions/os/FileExists
+    - functions/os/Getenv
+    - functions/os/ReadDir
+    - functions/os/ReadFile
+  returnType: os.FileInfo
+  signatures: [os.Stat PATH]
+aliases: [/functions/os.stat]
+---
+
+The `os.Stat` function attempts to resolve the path relative to the root of your project directory. If a matching file or directory is not found, it will attempt to resolve the path relative to the [`contentDir`](/getting-started/configuration#contentdir). A leading path separator (`/`) is optional.
+
+```go-html-template
+{{ $f := os.Stat "README.md" }}
+{{ $f.IsDir }}    → false (bool)
+{{ $f.ModTime }}  → 2021-11-25 10:06:49.315429236 -0800 PST (time.Time)
+{{ $f.Name }}     → README.md (string)
+{{ $f.Size }}     → 241 (int64)
+
+{{ $d := os.Stat "content" }}
+{{ $d.IsDir }}    → true (bool)
+```
+
+Details of the `FileInfo` structure are available in the [Go documentation](https://pkg.go.dev/io/fs#FileInfo).

docs/content/en/functions/os/_index.md

@@ -0,0 +1,12 @@
+---
+title: OS functions
+linkTitle: os
+description: Template functions to interact with the operating system.
+categories: []
+keywords: []
+menu:
+  docs:
+    parent: functions
+---
+
+Use these functions to interact with the operating system.