greater-than: add example (#16090)

pages/common/greater-than.md

@@ -1,6 +1,6 @@
 # Greater than
 
-> Redirect output to a file.
+> Redirect output.
 > More information: <https://gnu.org/software/bash/manual/bash.html#Redirecting-Output>.
 
 - Redirect `stdout` to a file:
@@ -22,3 +22,7 @@
 - Clear the file contents or create a new empty file:
 
 `> {{path/to/file}}`
+
+- Redirect `stderr` to `stdout` for piping them together:
+
+`{{command1}} 2>&1 | {{command2}}`