#!/usr/bin/env zsh
# Makes all files in <directory> lower case. Works with Non-ASCII characters.
# Equivalent to `zmv "${dir}/(*)" '${dir}/${1:l}'`

setopt LOCAL_OPTIONS ERR_RETURN NO_UNSET PIPE_FAIL

autoload -U die

[[ ${ARGC} -ne 1 ]] && die 1 "Usage: ${0} <directory>"
local dir="${1}"

for file in "${dir}"/*; do
    local basename="${file##*/}"
    local newfile="${dir}/${basename:l}"
    [[ "${file}" != "${newfile}" ]] && mv "${file}" "${newfile}" || :
done