[NBLUG/talk] Mutual exclusion in shell scripts?
sampln at sbcglobal.net
Sat Jan 20 16:07:33 PST 2007
I have the following shell script that I use to train spamassassin:
while [ -e /tmp/filter.lock ]
sa-learn $1 --no-sync
rm -f /tmp/filter.lock
Although multiple instances of the script may be called at the same time, I
only want one to be running at a given time. I do this because my mail
server isn't powerful enough to handle multiple instances of sa-learn
If a second or two passes between calls to the script, everything seems to
work OK. However, if the script is called several times in rapid succession,
filter.sh < msg1 & filter.sh < msg2 & filter.sh < msg3
Enough time passes between checking for /tmp/filter.lock and actually
setting /tmp/filter.lock that every instance of the script runs
simultaneously. Is there a way to avoid that?
Lincoln Peters <sampln at sbcglobal.net>
Many a man who thinks he's going on a maiden voyage with
a woman finds out later that it was just a shake-down cruise.
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