From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH iproute2 net-next 0/3] ss: Allow selection of columns to
 be displayed
Date: Tue, 30 Oct 2018 09:38:42 -0700
Message-ID: <20181030093842.0e174ea6@xeon-e3>
References: <cover.1540910943.git.sbrivio@redhat.com>
        <7ffc00c8-bdf6-5c75-564e-2663494bda5d@gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Cc: Stefano Brivio <sbrivio@redhat.com>,
        "Yoann P." <yoann.p.public@gmail.com>, netdev@vger.kernel.org
To: David Ahern <dsahern@gmail.com>
Return-path: <netdev-owner@vger.kernel.org>
Received: from mail-pf1-f193.google.com ([209.85.210.193]:44067 "EHLO
        mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1727008AbeJaBdH (ORCPT
        <rfc822;netdev@vger.kernel.org>); Tue, 30 Oct 2018 21:33:07 -0400
Received: by mail-pf1-f193.google.com with SMTP id j13-v6so2617534pff.11
        for <netdev@vger.kernel.org>; Tue, 30 Oct 2018 09:38:56 -0700 (PDT)
In-Reply-To: <7ffc00c8-bdf6-5c75-564e-2663494bda5d@gmail.com>
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Tue, 30 Oct 2018 10:34:45 -0600
David Ahern <dsahern@gmail.com> wrote:

> On 10/30/18 9:05 AM, Stefano Brivio wrote:
> > Now that we have an abstraction for columns, it's relatively easy to
> > selectively display only some of them, and Yoann has a use case for it.
> > 
> > Patch 1/3 fixes a rendering issue that shows up only when display of
> > arbitrary columns is disabled. Patch 2/3 implements the relevant option,
> > and patch 3/3 makes the output more readable when some columns are
> > disabled.
> > 
> >  
> 
> I like the intent, and I have prototyped something similar for 'ip'.
> 
> A more flexible approach is to use format strings to allow users to
> customize the output order and whitespace as well. So for ss and your
> column list (winging it here):
> 
>     netid          = %N
>     state          = %S
>     recv Q         = %Qr
>     send Q         = %Qs
>     local address  = %Al
>     lport port     = %Pl
>     remote address = %Ar
>     remote port    = %Pr
>     process data   = %p
>     ...
> 
> then a format string could be: "%S  %Qr %Qs  %Al:%Pl %Ar:%Pr  %p\n"
> 
> or for csv output: "%S,%Qr,%Qs,%Al,%Pl,%Ar,%Pr,%p\n"
> 
> I have not had time to look into an implementation for ip. Conceptually
> - and scanning the kernel's vsprintf code - it does not look that
> difficult, just time consuming on the frontend with the initial setup.

The problem with custom formats is that you lose all ability for Gcc
to check format strings.