[Mailman-Users] List Sync Problem

Greg Ward gward at mems-exchange.org
Tue Dec 4 15:56:30 CET 2001

On 04 December 2001, Jon Carnes said:
>  2) The following line (added to the script) may not work as you desire:
>     "cat /tmp/ise-all_list | grep -vi archive > /tmp/ise-all_list"
> You are outputing from the same file that you are inputing to... If it 
> can't do this in one read, then you may end up with a blank file.

That's almost certainly a problem.  I'm surprised the script works at
all.  Back when I was a Unix neophyte, I naively played around with that
sort of thing, and it always failed.  I'm pretty sure the shell does

  fopen("/tmp/ise-all_list", "w")

before "cat" even gets a chance to open it for reading.  (Possibly even
before it forks and execs cat.)

Hmmm: perhaps the shell forks and execs cat, and *then* opens
/tmp/ise-all_list for writing: bang, you've got a race condition, which
explains why the script sometimes works and sometimes fails.

Greg Ward - software developer                gward at mems-exchange.org
MEMS Exchange                            http://www.mems-exchange.org

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