macOS Delete All Local Snapshots

Single line at shell prompt …

$ for i in tmutil listlocalsnapshots / | egrep -o '\d{4}-\d{2}-\d{2}-\d+'; do sudo tmutil deletelocalsnapshots $i; done

In a bash/zsh script …

#!/bin/bash
for i in tmutil listlocalsnapshots / | egrep -o '\d{4}-\d{2}-\d{2}-\d+'
do
    sudo tmutil deletelocalsnapshots $i
done