[Xymon] Bug? procs test going red green every hour

[Jeremy Laidman]

Hmm, interesting. So it looks like the Xymon command is written to support
multi-line input, such as this sort of thing:

echo "status $HOST.test\\" > $TMPFILE # continued
echo "green \\" >> $TMPFILE # continued
echo "`date`\\" >> $TMPFILE # continued
echo "Test X is OK" >> $TMPFILE # not continued
echo "The test X was tested and found to be OK" >> $TMPFILE
$XYMON $XYMSRV < $TMPFILE

so that a single (eg status) line can be split over multiple input lines by
using backslash at EOL.

The code in stackio.c that joins lines due to a trailing backslash seems to
skip over any spaces immediately after the backslash (eg "first
line...\<sp><sp><sp><lf>...first line continued").

I note that "ps" displays the multi-line "sed" command with a trailing
space.

$ $ ps -f | sed '1i\
'|grep '[s]ed'|tr ' ' '.'
jeremyl...3104..2448..0.10:31.pts/3....00:00:00.sed.1i\.

There is no trailing space in the process args, so ps must be adding it.
Perhaps this is to de-fang any backslashes, precisely to avoid what seems
to be happening with the xymon client.

So perhaps "escaping" a "\<sp>" sequence at the end of a line would fix
this. Something like:

ps -Aww f -o pid,ppid,user,start,state,pri,pcpu,time:12,pmem,rsz:10,vsz:10,cmd
| sed 's/\\  *$/\\./'

J

On Sat, 23 Mar 2024 at 02:34, John Horne <john.horne at plymouth.ac.uk> wrote:

> On Fri, 2024-03-22 at 13:04 +0000, John Horne wrote:
> > On Fri, 2024-03-22 at 10:10 +1100, Jeremy Laidman wrote:
> > > This seems to be an artefact of the "xymon" command, perhaps sanitising
> > > input.
> > >
> > I would agree.
> >
> >
> Interestingly in the source lib/stackio.c (line 58) is the input comment:
>
> =====
>  * Simultaneously, lines ending with a '\' character are
>  * merged into one line, allowing for transparent handling
>  * of very long lines.
> =====
>
> Unfortunately I've got to leave work in a minute, but I would say this
> could be
> where the lines are merged. The comment comes from the 'unlimfgets'
> routine,
> which is used by the xymon command (common/xymon.c) to read input.
>
>
> John.
>
> --
> John Horne | Senior Operations Analyst | Technology and Information
> Services
> University of Plymouth | Drake Circus | Plymouth | Devon | PL4 8AA | UK
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