Add info for mktemp command

pages/04.other/useful-commands/default.en.md

@@ -152,3 +152,45 @@ touch -a -m -d "2023-07-29T00:23" <file>
 
 > [Linux - modify file modify/access/change time](https://stackoverflow.com/questions/40630695/linux-modify-file-modify-access-change-time)  
 > [How can I change the date modified/created of a file?](https://askubuntu.com/questions/62492/how-can-i-change-the-date-modified-created-of-a-file)
+
+### Create a random temporary directory / file
+
+Using `mktemp`, a randomly named file or directory will be created in `/tmp`
+
+Create a file:  
+[shuser]
+
+```sh
+mktemp
+```
+
+[/shuser]
+
+Create a directory:  
+[shuser]
+
+```sh
+mktemp -d
+```
+
+[/shuser]
+
+Save the output into an environment variable for future referencing
+
+sh / Bash:  
+[shuser]
+
+```sh
+export TMPDIR=$(mktemp -d)
+```
+
+[/shuser]
+
+Fish:  
+[shuser]
+
+```fish
+set TMPDIR (mktemp -d)
+```
+
+[/shuser]