A simple echo using the shell printf for consistent behavior

simple-echo.function.sh

#!/usr/bin/env sh

secho() {
    _arg="${1}";
    _fmt='%s';
    _sentinel='--';

    case "${_arg}" in
        (-e|-en|-ne) _fmt='%b'; shift ;;
        (-n|-En|-nE) shift ;;
        (-E|-Ee|-eE) shift ;;
        (-enE|-eEn|-nEe|-neE|-Een|-Ene) shift ;;
    esac;

    while [ "${#}" -gt 0 ]; do
        [ -n "${_sentinel}" ] &&
        [ "${1}" = "${_sentinel}" ] && {
            _sentinel='';
            shift;
            continue;
        };
        printf -- "${_fmt}" "${1}";
        [ "${#}" -gt 1 ] && {
            printf -- '%c' "${IFS- }"
        };
        shift;
    done;

    case "${_arg}" in
        (-n|-en|-ne|-En|-nE) : ;;
        (-enE|-eEn|-nEe|-neE|-Een|-Ene) : ;;
        (*) printf -- '\n' ;;
    esac;

    unset -v _arg _fmt _sentinel;
    return 0;
}