weird script behaviour

weird script behaviour

[urgrue]

i have script that runs ok from the prompt but doesnt run ok at all 
from cron (yes we've all seen this before, but this time its weirder 
than usually).
i even tried running it with env -i , but i cant reproduce the problem 
at the shell - it only appears when started from cron.
the problem also does NOT appear when started with "at".
i snipped the script down to a bare test minimum and am still able to 
reproduce the error, here it is:

#!/bin/bash

while true
do
sleep 1
echo "start" | logger
ping -n -c 1 -w 3 10.155.11.37 && continue
echo "we didnt continue..... | logger
done

point is to spot if a ping doesnt go.
run from the prompt, it works fine - it pings every second and i never 
get to the "we didnt continue" part.
run from cron, it may or may not run ok for a little while (a minute or 
so), but then it starts to repeatedly reach the "we didnt continue" 
part - and itll keep hitting that part over and over again until i 
intervene.
with a little extra checking, i found out that the ping isn't returning 
zero (as it does from the shell), but its returning 141! where does 
this come from? why does it only start appearing after a minute or so?

Re: weird script behaviour

[Jamie Harris]

How frequently does cron attempt to run the script?  Is there anything
between your and the destination that might not like a lot of pings
comming from/going to the same IP (because the script is running multiple
times) so it adapting its firewall to block you?

Seems unlikely but just a thought.

Jamie...

> i have script that runs ok from the prompt but doesnt run ok at all
> from cron (yes we've all seen this before, but this time its weirder
> than usually).
> i even tried running it with env -i , but i cant reproduce the problem
> at the shell - it only appears when started from cron.
> the problem also does NOT appear when started with "at".
> i snipped the script down to a bare test minimum and am still able to
> reproduce the error, here it is:
>
> #!/bin/bash
>
> while true
> do
> sleep 1
> echo "start" | logger
> ping -n -c 1 -w 3 10.155.11.37 && continue
> echo "we didnt continue..... | logger
> done
>
> point is to spot if a ping doesnt go.
> run from the prompt, it works fine - it pings every second and i never
> get to the "we didnt continue" part.
> run from cron, it may or may not run ok for a little while (a minute or
> so), but then it starts to repeatedly reach the "we didnt continue"
> part - and itll keep hitting that part over and over again until i
> intervene.
> with a little extra checking, i found out that the ping isn't returning
> zero (as it does from the shell), but its returning 141! where does
> this come from? why does it only start appearing after a minute or so?
>
> -
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>


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Re: weird script behaviour

[pacho baratta]

Il ven, 2003-05-23 alle 14:48, urgrue ha scritto:
> i have script that runs ok from the prompt but doesnt run ok at all 
> from cron (yes we've all seen this before, but this time its weirder 
> than usually).
> i even tried running it with env -i , but i cant reproduce the problem
> at the shell - it only appears when started from cron.
> the problem also does NOT appear when started with "at".
> i snipped the script down to a bare test minimum and am still able to 
> reproduce the error, here it is:
> 
> #!/bin/bash
> 
> while true
> do
> sleep 1
> echo "start" | logger
> ping -n -c 1 -w 3 10.155.11.37 && continue
> echo "we didnt continue..... | logger
> done
> 
> point is to spot if a ping doesnt go.
> run from the prompt, it works fine - it pings every second and i never
> get to the "we didnt continue" part.
> run from cron, it may or may not run ok for a little while (a minute
or 
> so), but then it starts to repeatedly reach the "we didnt continue" 
> part - and itll keep hitting that part over and over again until i 
> intervene.
> with a little extra checking, i found out that the ping isn't
returning 
> zero (as it does from the shell), but its returning 141! where does 
> this come from? why does it only start appearing after a minute or so?

the script is not good here's the prob.

u say 
echo "we didnt continue..... | logger

without an "if...then" it's always true, so u always do echo "we
didn't..."

i'd better wrie so:

#!/bin/sh
while true
do
sleep 1
echo "start" | logger
if ping -n -c 1 -w 3 10.155.11.37
then echo "ping works and host is up, man!!" | logger
else echo "ping what?? is network up? is that host up??" | logger
fi
done

regards, pacho



-- 
pacho baratta			IT Consultant
tel. +39 347 078.51.31		www.evolinux.it
mail: pachox@evolinux.it