Note that "read -s" is not POSIX, and thus is not portable. The only allowed argument to POSIX read is "-r" which is enforced in Debian/Ubuntu by the dash syst

Note that "read -s" is not POSIX, and thus is not portable. The only allowed argument to POSIX read is "-r" which is enforced in Debian/Ubuntu by the dash system shell. https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/utilities/read.html https://pubs.opengroup.org/onlinepubs/9699919799.2018edition...