That's an *extremely* inefficient way of doing it (not to mention that cat's -t and -e are GNU extensions and may not be available).
If you really want to go that route, then do:

tail -n1 testfile | cat -te | grep -q \\\$$

Thanks.

The sed method is not realiable: for example, it does not work with GNU sed (even replacing -E with its equivalent in GNU sed -r). And besides that, sed needs to read the whole file, which is something that we specifically want to avoid. Along the same lines,

awk 1 file

which is mentioned in the article, produces correct output regardless of whether the input has a trailing newline or not. But again, that needs to read the whole file.

And regarding the ed solution: it still reads the whole file so it's out of the article's scope, but it does work. It can be rewritten more portably as

printf '%s\n' H '$s/\(.*\)/\1/' w q | ed file

which, at least on GNU ed, prints a "Newline appended" message to let the user know what it did.

# note: ed will read entire file into memory
[[ -s file ]] && ed -s file <<< $'H\n$s/\(.*\)/\\1/\nwq'

sed -E -i "" '$s/(.*)/\1/' file

Hi Gregor,

thanks for the comment. Yes that will work, perhaps a bit heavyweight (3 processes) but it's good to list alternatives.