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Date:      Sat, 29 Jul 2023 19:28:13 +0000
From:      "Piotr P. Stefaniak" <pstef@freebsd.org>
To:        Jamie Landeg-Jones <jamie@catflap.org>
Cc:        freebsd-current@freebsd.org
Subject:   Re: ps(1) bugs and problems
Message-ID:  <ZMVoTXZKgKImgm22@freefall.freebsd.org>
In-Reply-To: <202307282307.36SN7b7v026284@donotpassgo.dyslexicfish.net>
References:  <202307282307.36SN7b7v026284@donotpassgo.dyslexicfish.net>

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On 2023-07-29 00:07:37, Jamie Landeg-Jones wrote:
>I have a program that produces a list of PIDS, that are supplied via '-p'
>to /bin/ps and are sorted with '-d'.

What language is it written in? What is the use case?

>After a late upgrade on a particular machine, I've just been bitten
>by the modifications to "ps" to unconditionaly add recurive descendancy
>PID lookups to the '-d' option when a pid is specified.

I understand that the behavioral change affected programs/scripts in a
way that requires adjustment and I do try to limit that as much as
possible. But this feature was a needed one and I thought it should
"just work" when -d was combined with -p, as opposed to adding a new
flag to the program.

Now that you've corrected my thinking, I plan to revert that change and
re-introduce the feature as a separate option, see
https://reviews.freebsd.org/D41231 for review.

>There is nothing in the man pages or docs to suggest that this should
>be a thing, but there you go.

I intend to revert the change so there's no plan to update this in the
manual page.

>Rather than just patch it out, Would a patch to allow the previous
>behaviour as an option (even if the option isn't default) be accepted?

Feel free to discuss D41231 or provide an other patch.

>In addition, there is a bug in that ps now goes into a memory-sucking
>endless-loop if you do:
>
>ps -dp0

Thanks for this report, it was an oversight of the corner case that the
parent PID of the PID 0 is also 0.

>The manual page is no longer accurate either:
>
>'-d' says "Note that this option has no effect if the “command”
>column is not the last column displayed."
>
>That is no longer true, it doesn't matter what column is displayed last,
>if you use '-p', '-d' now completely changes the output
>
>title: ps: extend the non-standard option -d (tree view) to work with -p
>https://cgit.freebsd.org/src/commit/bin/ps/ps.c?id=ca8c0d5e811048ad67d0955642c5b486e9c0f3d2
>
>author: Piotr Pawel Stefaniak <pstef@FreeBSD.org> 2020-05-07 16:56:18 +0000
>commit: ca8c0d5e811048ad67d0955642c5b486e9c0f3d2 (patch)
>tree:   374be17aead18daf2e3c7477a4573f60ce62d8f0 /bin/ps/ps.c

My plan is to revert that.

Piotr



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