Update ubuntu.md

Author: nicholaswilde

docs/ubuntu.md

@@ -95,8 +95,13 @@ sudo sed -i 's/#$nrconf{restart} = '"'"'i'"'"';/$nrconf{restart} = '"'"'a'"'"';/
 usermod -a -G adm,cdrom,lpadmin,sudo,sambashare,dip,plugdev nicholas
 ```
 
+## [Autocomplete Directories][6]
+
+`export CDPATH=foo`
+
 [1]: <https://fedingo.com/how-to-remove-snap-in-ubuntu/>
 [2]: <https://stackoverflow.com/questions/73034540>
 [3]: <https://veducate.co.uk/ubuntu-apt-update-fails/>
 [4]: <https://askubuntu.com/a/1421221/344358>
 [5]: <https://askubuntu.com/a/1381087>
+[6] <https://superuser.com/a/571778>