POSIX specifies that pr -f shall "[p]ause before beginning the first page if the standard output is associated with a terminal" (see https://pubs.opengroup.org/onlinepubs/9699919799/utilities/pr.html). GNU pr does not do this.
[The recently reported bug#47243 (https://lists.gnu.org/archive/html/bug-coreutils/2021-03/msg00033.html) made me look again at the POSIX specification for pr where I noticed this.] Thanks, Erik
