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Re^6: How to tell a child what to do?

by Anonymous Monk
on Sep 21, 2005 at 12:25 UTC ( #493755=note: print w/ replies, xml ) Need Help??


in reply to Re^5: How to tell a child what to do?
in thread How to tell a child what to do?

I've played with the code a bit more, and it's failing for me as well. But not always. How often it fails, depends on the number of spawned children. Trying 1, 2, 3, 4, and 5 children, each 10 times, I get success rates of 100%, 90%, 40%, 10% and 0%.

Something is wrong, but I do not know what. I'll have to consult Stevens.


Comment on Re^6: How to tell a child what to do?
Re^7: How to tell a child what to do?
by Eyck (Priest) on Sep 23, 2005 at 07:07 UTC
    I think, that if you rewrite this with sysread/syswrite, or, like in merlyn's solution with length-based communication, it starts working.

    This may have something to do with perl's buffering, in particular, when instead of while (<>) I wrote this:

    my $q; $q=<STDIN>; print "Received(child $$): $q\n";
    it stopped hanging on close($fd).

    When I traced what is happening when it hangs, it looks like parent is waiting waitpid(..) (close($fd) on pipe is supposed to do that), while child blissfully unaware is running read...

    Now I can safely go and try to understand merlyn's code.

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