dhcpcd-discuss

Hi

On 09/01/2018 00:33, Barry Kauler wrote:
> Hi,
> Have just joined the list.
>
> I have used dhcpcd for years, for Puppy Linux, however, fairly
> recently something odd happened.
>
>   DHCPCDFIX="-I ''"
>   MODTIME1="`stat --format=%Y /etc/resolv.conf`"
>   dhcpcd $DHCPCDFIX $INTERFACE
>   sleep 0.1
>   MODTIME2="`stat --format=%Y /etc/resolv.conf`"
>   [ "`grep -v '^#' /etc/resolv.conf`" == "" ] && MODTIME2="$MODTIME1" #fail.
>
>   if [ "$MODTIME2" != "$MODTIME1" ];then
>
> In the above code, I had to introduce that "sleep 0.1". Without it, I
> was sometimes getting MODETIME2 the same as MODTIME1, even though
> dhcpcd had succeeded.
>
> How could this problem even be possible? Unless /etc/resolv.conf is
> written-to asynchronously or as a separate process, and dhcpcd exits
> before the write happens?
>
> Or, does bash start executing the next line before dhcpcd completes?

No, bash does not start executing the nest line.
dhcpcd will hand off writing resolv.conf to a separate process as 
documented in dhcpcd-run-hooks(8) and it's not async.

To see what dhcpcd is doing, add this to the top of /etc/dhcpcd.conf

debug
logfile /var/log/dhcpcd.log

Then redo your test.
You can examine /var/log/dhcpcd.log to see what dhcpcd did. It won't 
document what each call out to dhcpcd-run-hooks does beyond the reason 
but it might answer your query.

Roy