[Gllug] Arithmetic error in bash on 08 and 09?

[Wulf Forrester-Barker]

Rich <rich at annexia.org> replied:

> 08 is an invalid octal number.  You need to change the script to
> remove the preceeding zero, so you're calculating in decimals.

09 as well. I've got a scripted routine on one of my boxes that ran into
exactly the same problem, calculating a log file name which was in the
format XXX[week of year + 1].log.

Of course, because it's based on the week of the year, the system ran
smoothly for several months before this bug reared its ugly head.
Fortunately I got onto it right away otherwise the symptoms might have
disappeared before I became any the wiser.

Originally, I'd been using:

Xfile="XXX$(( $(date +%U)+1 )).log"

This has now been patched to:

if [ $(date +%U) = "08" ]; then
	Xfile="XXX9.log"
elif [ $(date +%U) = "09" ]; then
	Xfile="XXX10.log"
else
	Xfile="XXX$(( $(date +%U)+1 )).log"
fi

It's not incredibly elegant but, along with a nice fat comment, it
serves to keep the issue in mind next time I do something that might be
affected.

Out of interest, is there a neater way this could be done in a bash
script?

Wulf

-- 
Wulf Forrester-Barker, webmaster
http://www.lewisham.nhs.uk/


wulf.f-b at uhl.nhs.uk

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