[ntp:questions] Local clock question with dialup connection

Steve Kostecke kostecke at ntp.isc.org
Tue Apr 24 01:37:00 UTC 2007

On 2007-04-23, Nigel Henry <cave.dnb at tiscali.fr> wrote:
> On Monday 23 April 2007 22:20, Steve Kostecke wrote:
>> #!/bin/sh
>> # The hostname or IP address of the host that you want to ping.
>> while [ 1 ]

Start an infinite loop consisting of the statements between the 'do' and

>> do
>>   /bin/ping -c 4 $TARGET 2>/dev/null >/dev/null && break

&& is a command operator which denotes an AND list. An AND list has the

	command1 && command2

command2 is executed if, and only if, command1 returns an exit status of
zero. 'man bash' for more information.

So, in the line quoted above ...

Ping the $TARGET 4 times throwing away all output. Break out of the loop
if the ping is successful. Otherwise continue to the next step.

>>   /bin/sleep 60
>> done
>> /usr/local/bin/ntp-restart

The ntp-restart line is the only thing left to execute after breaking
out of the loop.

Steve Kostecke <kostecke at ntp.isc.org>
NTP Public Services Project - http://ntp.isc.org/

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