Comment by LegionMammal978

At least the GNU version of wc [0] uses AVX2 for line counting, if available. Though it falls back to a simple character-by-character loop if you ask for a character count [not to be confused with a byte count!] or a word count.

[0] https://git.savannah.gnu.org/cgit/coreutils.git/tree/src/wc_...