[ILUG] Slightly Off Topic : Concurrent Access to a Text File in a bash script - can I enforce thread safety

[la la]

It's better change to python, use multi-threads and mutex or sem to complete
your
work


On 7/13/07, Oisin Kim <oisinkim at gmail.com> wrote:
>
> Hi All,
>
> not a linux question, but I know there are some bash experts out there, so
> hope this can be answered by someone.
>
> Basically I have a very simple script, it will generate checksums for some
> files and write the details to a log file, since the number of files is
> small, and the server has a will have a large number of CPUs I'd like to
> run
> the checksums in parallel.
>
> What concerns me is how I can be sure that writes to the log file are
> "thread safe", so that different processes don't corrupt the entries.
>
> I've not been able to get any process writing to the file to overlap, but
> that was on a limited test of 1000 files, and on my laptop.
>
> Something as simple as this:
>
> for i in *.* do
>    cksum $i >> log.file &
> done
>
> So far I can't get two cksum processes to overlap each other in the
> log.file,
> but I understand this might be hardware/file numbers.
>
> I googled around and couldn't find something that answered this, so sorry
> if
> I am asking a dumb question!
>
> Thanks in advance,
> Oisin
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