I need to process a very large set of data. Currently it gets dumped from a database, is processed by a single-threaded perl script, and is loaded back into the database (the script does data validation). This currently takes about 3 hours. I was thinking of writing something that splits the file up and divides the task, but I was struck by this line (in http://perldoc.perl.org/perlfork.html) "Any filehandles open at the time of the fork() will be dup()-ed. Thus, the files can be closed independently in the parent and child, but beware that the dup()-ed handles will still share the same seek pointer. Changing the seek position in the parent will change it in the child and vice-versa." So, does this mean I can open this huge file, fork() a bunch of processes that each process individual lines, and thus creating a very terse multi-threaded file processor? I'm thinking there could be race conditions on the output, but if each fork writes it's own output file and these are aggregated after all children are done (and duplicate processing may be irrelevant)... why wouldn't that work???

In reply to Will a shared filehandle processed by multiple threads/processes cause problems? by alanraetz

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