Paul Eggert <eggert@cs.ucla.edu> writes:

> On 2025-07-28 10:36, Collin Funk wrote:
>> I don't really like the idea of changing '-f' depending on whether
>> POSIXLY_CORRECT is defined. So I would prefer this as well.
>
> On second thought (sorry...) I now think I understand why GNU pr
> behaves the way it does. The GNU coding standards[1] say "...please
> don’t make the behavior of a command-line program depend on the type
> of output device it gets as standard output or standard input. Device
> independence is an important principle of the system’s design; do not
> compromise it merely to save someone from typing an option now and
> then."
>
> The standards go on to list some exceptions, such as 'ls'. 'pr' is not
> one of the exceptions. Currently there are a few other exceptions in
> Coreutils ('df', 'mv', 'nohup', 'rm', 'tail') but I guess 'pr' didn't
> make the cut when it was written.
>
> That is, my theory is that when GNU 'pr' was written, its original
> author Pete TerMaat followed the GNU coding standards, and
> deliberately made '-f' and '-F' aliases, because that way the behavior
> of pr would not depend on isatty (STDOUT_FILENO). And Pete did not
> implement -p because it didn't sound useful if we follow the coding
> standards.
>
> If this theory is correct, then a fix that would be more in the spirit
> of GNU would be something like this:

Interesting, I did not know about this part of the GNU Coding Standards.

> (a) Implement -p as if isatty (STDOUT_FILENO) is true. This form of -p
> is useful only when stdout is a terminal, but that's good enough since
> nobody uses (or will use :-) -p.
>
> (b) If POSIXLY_CORRECT is set, change -f and -p so that they both
> worry about isatty (STDOUT_FILENO), as POSIX requires.
>
> This would conform to POSIX, would address Pádraig's concern about
> compatibility, and would follow the GNU coding standards.

That sounds good to me. I attached a v4 patch that should behave this
way and address the other issues that you mentioned.

> It'd be less useful in practice, but that doesn't matter since the
> practical need for this behavior vanished decades ago.

Thanks for again for the thorough review and explanations. I find it
funny that I assumed this change was simple and learned it's purpose was
for logging in on a teletype. The Model 37 predates me ~30 years, so it
never occured to me that the purpose was to not print logins.

Collin