How to Secure erase files in OS X without moving the files into trash?

1. Open the Terminal.app (Found in /Applications/Utilities).
2. Type cd  and drag the folder which contains the file you want to delete, to the terminal window.
3. Type rm -P FileName.extension and hit Enter

https://apple.stackexchange.com/questions/57879/how-to-secure-erase-files-in-os-x-without-moving-the-files-into-trash

Linux - srm

https://www.howtogeek.com/425232/how-to-securely-delete-files-on-linux/