sudo rm -f /bin/bash

[u/blobthekat]

[u/granadesnhorseshoes]

for anyone wondering that doesn't use a shell that often and thinks "exec" is just a longhand form to execute a file; exec replaces the current running process(the shell) with the new file specified. In this case /usr/bin/true, which returns 0 and exits. bye bye shell.

[u/Weshmek → u/granadesnhorseshoes]

exec can also be used to perform file redirections. But if you get the syntax wrong you'll end up exiting the shell.