Question: I want a command to shred completely the contents of a folder/directory (which may be inside folders/directories).
Also please explain the command.

Answer: 
1. Install the package `secure-delete`.
2. Use the command `srm -r pathname` to remove your folder and files.

The default settings are for 38 (!!!) passes of overwrites which is extreme overkill imho (see more info about this [here](https://web.archive.org/web/20120409055439/http://www.anti-forensics.com/disk-wiping-one-pass-is-enough)).

For my usage, I only want a single pass of random data so I use `srm -rfll pathname`.

If you want to create a right-click option in the GUI for files and folders, use gnome-actions to call a script like this:

```
#!/bin/bash
if dialog=`zenity --window-icon=warning --question --title="Secure Delete" --no-wrap --text="Are you sure you want to securely delete:\n\n     $1\n\nand any other files and folders selected? File data will be overwritten and cannot be recovered."` 
then /usr/bin/srm -fllrv "$@"| zenity --progress --pulsate --text="File deletion in progress..." --title="Secure Delete" --auto-close
fi 

```

If you want more paranoid settings be sure to modify the above script.
When I need to shred multiple files or an entire directory I simply use `shred -vzn 20 ./shredme/*.*` for example, which overwrites all files with any file extension in the "shredme" folder. Then you can use the standard rm -rf ./shredme command to remove the folder itself (or just right click and delete the folder) as all the data has been overwritten 20 times for this example.

I did a quick example of this with a bunch of duplicate images as an example. 

![Terminal screenshot](https://i.stack.imgur.com/s9ULy.png)