SOLVED: weird script behaviour

SOLVED: weird script behaviour

[urgrue]

well, it seems that i have to do it like this:
ping -n -c 1 -w 3 10.155.x.y >/dev/null && continue

so far it seems that this way it will correctly pass 0 (and thus 
"continue") if the ping goes, and something else if it doesnt (and thus not 
"continue").
what was happening was that, without the >/dev/null, the ping will send 0 
roughly 14 times (why 14???) and then it starts passing 141!!

if anyone can tell me why this happens, and where that 141 comes from, id 
be happy.
there is no 141 in ping's output, and ping's return code ($?) is always 0, 
1, or 2 (was during my  tests, anyway). so i really dont get where that 141 
comes from.



>A feature of running commands under 'at' is that 'at' includes the
>environment that is current when you issue the 'at' command ... unlike cron,
>which doesn't know squat about more than the basic environment.
>
>Rather than use 'bash,' why not try /bin/ksh?  bash may have some
>requirements that are getting interfered with because it's cron running it.
>I know you may be using 'bash' as your primary shell, but humor me.  Cron
>likes bsh and ksh and most times csh.  Other times, it may have problems.
>
>Something that I've practiced since I started and has never failed me is to
>try to code scripts and programs for the minimum number of features
>necessary by using bsh where possible, ksh where necessary, and almost never
>anything else (and to hard-code 'cron' entries as much as possible).  In
>this way, conservative does the trick.  Sometimes you can't avoid other
>programs, but most times you can.
>
>Ok.  Soapbox away ... sorry about the suds.
>
>
>----------------------------------
>Bruce T. Harvey (Special Projects)
>----------------------------------------
>bth@comcast.net  -- bruceh@routescape.com
>443-465-1204 (personal) -- 410-403-2390 (office)
>-------------------------------------------
>Insight Distribution Systems / CoAxis, Inc.
>Hunt Valley, Maryland  U.S.A.  21031-1422
>-------------------------------------------
>
>
>
>
>
>-----Original Message-----
>From: urgrue [mailto:urgrue@tumsan.fi]
>Sent: Friday, May 23, 2003 8:49 AM
>To: linux-admin@vger.kernel.org
>Subject: weird script behaviour
>
>
>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?
>
>-
>To unsubscribe from this list: send the line "unsubscribe linux-admin" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: SOLVED: weird script behaviour

[Venkat Raju]

The return value of a process if it is terminated by a signal is
(128 + signal_number). Looks like ping is terminating on signal
13 SIGPIPE (Broken pipe: write to pipe with no readers).

Venkat

On Fri, May 23, 2003 at 08:57:03PM +0300, urgrue wrote
> well, it seems that i have to do it like this:
> ping -n -c 1 -w 3 10.155.x.y >/dev/null && continue
> 
> so far it seems that this way it will correctly pass 0 (and thus 
> "continue") if the ping goes, and something else if it doesnt (and thus not 
> "continue").
> what was happening was that, without the >/dev/null, the ping will send 0 
> roughly 14 times (why 14???) and then it starts passing 141!!
> 
> if anyone can tell me why this happens, and where that 141 comes from, id 
> be happy.
> there is no 141 in ping's output, and ping's return code ($?) is always 0, 
> 1, or 2 (was during my  tests, anyway). so i really dont get where that 141 
> comes from.
> 
> 
> 
> >A feature of running commands under 'at' is that 'at' includes the
> >environment that is current when you issue the 'at' command ... unlike 
> >cron,
> >which doesn't know squat about more than the basic environment.
> >
> >Rather than use 'bash,' why not try /bin/ksh?  bash may have some
> >requirements that are getting interfered with because it's cron running it.
> >I know you may be using 'bash' as your primary shell, but humor me.  Cron
> >likes bsh and ksh and most times csh.  Other times, it may have problems.
> >
> >Something that I've practiced since I started and has never failed me is to
> >try to code scripts and programs for the minimum number of features
> >necessary by using bsh where possible, ksh where necessary, and almost 
> >never
> >anything else (and to hard-code 'cron' entries as much as possible).  In
> >this way, conservative does the trick.  Sometimes you can't avoid other
> >programs, but most times you can.
> >
> >Ok.  Soapbox away ... sorry about the suds.
> >
> >
> >----------------------------------
> >Bruce T. Harvey (Special Projects)
> >----------------------------------------
> >bth@comcast.net  -- bruceh@routescape.com
> >443-465-1204 (personal) -- 410-403-2390 (office)
> >-------------------------------------------
> >Insight Distribution Systems / CoAxis, Inc.
> >Hunt Valley, Maryland  U.S.A.  21031-1422
> >-------------------------------------------
> >
> >
> >
> >
> >
> >-----Original Message-----
> >From: urgrue [mailto:urgrue@tumsan.fi]
> >Sent: Friday, May 23, 2003 8:49 AM
> >To: linux-admin@vger.kernel.org
> >Subject: weird script behaviour
> >
> >
> >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?
> >
> >-
> >To unsubscribe from this list: send the line "unsubscribe linux-admin" in
> >the body of a message to majordomo@vger.kernel.org
> >More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-admin" in
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>