Remove last line from really big files

trim.sh

#!/bin/bash
# credits:
# https://stackoverflow.com/a/17794626/16157358
# https://stackoverflow.com/questions/4881930/remove-the-last-line-from-a-file-in-bash

### NOT DONE BY ME, JUST KEEPING FOR POSTERITY
filename="example.txt"

file_size="$(stat --format=%s "$filename")"
trim_count="$(tail -n1 "$filename" | wc -c)"
end_position="$(echo "$file_size - $trim_count" | bc)"

dd if=/dev/null of="$filename" bs=1 seek="$end_position"

Or alternatively, as a one liner:

dd if=/dev/null of=<filename> bs=1 seek=$(echo $(stat --format=%s <filename> ) - $( tail -n1 <filename> | wc -c) | bc )