Securely delete a file in MacOS

I have a file containing a private key that I want to securely delete. [Several](https://www.groovypost.com/howto/securely-delete-files-mac/) [sites](https://macpaw.com/how-to/secure-erase-files-on-macos) as well as Claude suggest using rm -P but the man page of rm says: This flag has no effect. There was also a suggestion about "Secure empty the trash" which is an option that has been removed. Is there a simple way to securely delete the file (preferrably from the command line)?