erratic sh arithmetic

[Karl Auer]

On Thu, 2020-07-09 at 21:21 -0600, Gary Aitken wrote:
> I'm seeing crazy erratic behavior in sh arithmetic executing in
> a cron script as root:

Haven't looked closely, but any value beginning with "0" is regarded as
octal, so 08 (also 09, 18, 19, 28 and 29) should be throwing "value too
great for base".

week=$(( ( 8 + 6 - 3 ) / 7 + 1 ))

works for me, but

week=$(( ( 08 + 6 - 3 ) / 7 + 1 ))

Results in:

bash: ( 08: value too great for base (error token is "08")

If it's been up for two weeks, running daily, you should have had a
similar error on 28 and 29 June.

BTW,

week=`expr \( 08 + 6 - 3 \) / 7 + 1`

works for me too, which I have to say was a bit of a surprise, I
expected expr to understand octal, and my doco for expr says it does
too. But this returns 3; if it understood octal it would return 2:

week=`expr \( "011" + 6 - 3 \) / 7 + 1`

Regards, K.

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Karl Auer (kauer at biplane.com.au)
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