On Thu, 24 Dec 2020 16:32:18 +0100
tito via Dng <dng@???> wrote:

> On Thu, 24 Dec 2020 10:10:07 -0500
> Steve Litt <slitt@???> wrote:
>
> > On Wed, 23 Dec 2020 23:41:58 +0100
> > Didier Kryn <kryn@???> wrote:
> >

> > > Le 23/12/2020 à 22:03, Antony Stone a écrit :  
> > > > If the kernel decides A=eth1, B=eth2, C=eth0 then there's no way
> > > > for udev rules to rename them, because "File exists" (which
> > > > should of course say "Device name exists").    

> > >
> > >     This should not happen and did not happen in the past because
> > > the interfaces are created sequentially.
> >
> > Yes it did. It happened in the 1900's. We were all advised never to
> > use the same type of network card for both interfaces, because which
> > card became eth0 would be indeterminate. I had eth0 magically switch
> > to eth1, and then back again, several times.
> >
> > Earlier in this thread I submitted a shellscript that fixes this
> > whole problem, without all sorts of udev raindances.
> >
> > SteveT
> >
> > Steve Litt
>
> Hi,
> is it this one? How does it solve my problem to rename
> interfaces according to their mac address without
> name collisions (plus corner cases)?
>
> #!/bin/sh
> # Copyright (c) 2016 by Steve Litt
> # Expat license. See http://directory.fsf.org/wiki/License:Expat
>
> chosen_wifi_number=${1:-1}
> wifidevs=0
>

> for dev in `ip -o link | sed -n 's/[^:]*: *\(w[^:]*\).*/\1/p'`;
> do
>     wifidevs=`expr $wifidevs + 1`

>

>     test $wifidevs -eq $chosen_wifi_number && {
>     echo $dev
>     exit 0
>     }
> done

>
> echo =max$wifidevs
>
> Ciao,
> Tito


It either is the one, or looks a whole lot like it.

Note that somebody else on this list made it even better, but I can't
find that email again.

If the "w" in the sed command is changed to "e", then it does the same
thing for wired Ether net.

The shellscript I wrote spits out one answer. However, it could easily
be modified to do several, either letting you choose, or perhaps if
running exec'ed or dotted, create environment vars like eth0, eth1,
eth2, etc, and wlan0, wlan1, wlan2, etc, so all you need to do in your
shellscripts is change "wlan0" to "$wlan0". As long as nobody switches
slots or jacks, the numbering of these will be determinate.

SteveT

Steve Litt
Autumn 2020 featured book: Thriving in Tough Times
http://www.troubleshooters.com/thrive