Re: [FWP] Puzzle - Temp file creation

[Chaim Frenkel <chaimf@pobox.com>]

>>>>> "MGS" == Michael G Schwern <schwern@pobox.com> writes:

MGS> And several copies of that program are running at the same time (say
MGS> its a CGI program on a high-load web server).  What happens when two
MGS> of them get run in the same second?  Ooops.

MGS> open(TMP, ">foo".time.$$"); isn't even safe, because if your program
MGS> is running persistantly (say as a daemon or under mod_perl or FastCGI)
MGS> subsequent runs will have the same PID, and if it runs twice in the
MGS> same second (a strong possibility), you're screwed.

I still don't see the need for the search. Temporary files are
temporary, (duh).

If it is possible that the process is still alive when it gets around
to stepping on its own foot, then a monotonically increasing counter
would be perfect.

If there is a race condition possible, split them up. I'm partial to
mkdir "tempdir.$$". sticking hostname in there, if multiple hosts are
sharing this.

The pid can't be reused as long as the process is still around, so
the kernel will take care of the locking.

<chaim>
-- 
Chaim Frenkel					     Nonlinear Knowledge, Inc.
chaimf@pobox.com				               +1-718-236-0183

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