<: add here strings and documents (#13988)

pages/common/less-than.md

@@ -1,9 +1,16 @@
 # Less than
 
-> Redirect a file to `stdin`.
-> Achieves the same effect as `cat file.txt |`.
+> Redirect data to `stdin`.
 > More information: <https://gnu.org/software/bash/manual/bash.html#Redirecting-Input>.
 
-- Redirect a file to `stdin`:
+- Redirect a file to `stdin` (achieves the same effect as `cat file.txt |`):
 
 `{{command}} < {{path/to/file.txt}}`
+
+- Create a here document and pass that into `stdin` (requires a multiline command):
+
+`{{command}} << {{EOF}} <Enter> {{multiline_data}} <Enter> {{EOF}}`
+
+- Create a here string and pass that into `stdin`:
+
+`{{command}} <<< {{string}}`