Unix Programming - Re: Concurrent Updates of the Same File by 2 Instances of the Same

Author

Re: Concurrent Updates of the Same File by 2 Instances of the Same

Ralf Fassel

2006-02-17, 10:40 pm

* "John Smith" <wleung7@gmail.com>
| if i use a lockfile, i can only restrict access to the file by
| terminating the S2. How do I make S2 "busy-wait" for S1 to finish
| such that S1 and S2 are serialized?

procmail (http://www.procmail.org/) has a 'lockfile' binary which
creates the lockfile in an atomic fashion. Probably the OS has
something like that?

If you use a non-atomic wait a la
while test -f lockfile ; do
sleep 1
done
touch lockfile
you will get bitten by the race condition sooner or later.

R'