Re: Sporadic superfluous successful exits

[Jim Meyering]

Aki Helin wrote:
> For some reason Grep appears to occasionally exit with 0 even when there
> was no match. This could also be bug Bash, but I wasn't able to reproduce
> this with other programs, and the failure seems to be more common with
> some patterns, or pairs of a pattern and an input, which would suggest
> that the issue is in Grep.
>
> The following is enough to eventually reproduce this on Debian 6.0.4
> (x86_64) using the included version (GNU grep 2.6.3) and 2.10 from
> ftp.gnu.org. The shell is Bash is version 4.1.5(1)-release.
>
>  $ wget haltp.org/aoh/misc/cout.sh
>  $ while true; do grep RANDOM cout.sh && date; done
>
> Nothing should happen, but I'm getting occasional dates as in
>
>  $ while true
>  > do
>  > grep -q RANDOM tests/cout.sh && date
>  > done
>  Wed Feb  8 05:52:23 EET 2012
>  Wed Feb  8 06:28:02 EET 2012
>
> and for Grep 2.10
>
>  $ while true; do $HOME/opt/grep/bin/grep RANDOM tests/cout.sh && date; done
>  Wed Feb  8 14:56:00 EET 2012
>
> Can anyone reproduce this, and if so, does it look like a Grep thing or
> something else?

Can you reproduce that on more than one system?

With such low frequency, I would suspect your system's RAM or other
hardware.  I had a system that was 100% reliable for about six years,
but then a few of the big capacitors near the CPU began (very slowly)
to bulge and even to leak a little.  By the time 5 or 6 were bulging,
I began to see errors and the occasional crash, usually only accompanying
heavy disk or network activity.

I've started one of your loops on a debian unstable system using
grep-2.10 and zsh.  I will let it run for a few hours.