From mboxrd@z Thu Jan  1 00:00:00 1970
From: Duncan Roe <duncan_roe@optusnet.com.au>
Subject: Re: testing if a named set exists?
Date: Sat, 2 Oct 2021 12:52:45 +1000
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Sender: Duncan Roe <duncan.roe2@gmail.com>
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To: Matt Zagrabelny <mzagrabe@d.umn.edu>
Cc: Netfilter <netfilter@vger.kernel.org>

On Fri, Oct 01, 2021 at 08:16:17PM -0500, Matt Zagrabelny wrote:
> Hello,
>
> I'd like to do something like the following:
>
> if exists $named_set
>     nft add rule ip filter output ip daddr $named_set accept
> else
>     nft add rule ip filter output ip daddr $default_set accept
>
> Does anyone know if I can accomplish this with nftables?
>
> Thanks,
>
> -m
How about

> if nft list ruleset | grep -q "$named_set"; then
>   nft add rule ip filter output ip daddr $named_set accept
> else
>   nft add rule ip filter output ip daddr $default_set accept
> fi

You can restrict the search to a table, e.g. instead of "ruleset"
put "table $my_table"

Cheers ... Duncan.