in reply to Re^8: Win32: Setting a layer with binmode causes problem with close() on Windows (PerlIO silently fails to close the file)
in thread Win32: Setting a layer with binmode causes problem with close() on Windows

Please elucidate? (Preferably demonstrate.)

Its hard (cant test ATM), but it goes like this,
apache2 on win32 runs tracertfrontend.cgi which does  system 1, logtracertwithipcrun3.pl and redirects,
except logtracertwithipcrun3.pl blocks tracertfrontend.cgi

even if longtracertwithipcrun3.pl does another system 1... itself, STDIN/STDOUT/STDERR handles are still inherited (despite 0 flag), and it still blocks tracertfrontend.cgi

This scenario can work from (cmd.exe) console (no blocking), but not under whatever environment apache sets up (something like without console )

Proc::Background::Win32 tries to launch without inheriting handles, but it still blocks under apache

Win32::Process::Create/DETACHED_PROCESS combo seems to keep tracertfrontend.cgi from being blocked under apache

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Re^10: Win32: Setting a layer with binmode causes problem with close() on Windows (PerlIO silently fails to close the file)
by BrowserUk (Patriarch) on Jun 17, 2013 at 14:45 UTC
    This scenario can work from (cmd.exe) console (no blocking), but not under whatever environment apache sets up (something like without console )

    The problem is apache -- actually most webservers -- in that they do not forward the output from CGI processes until (all copies of) both STDOUT and STDERR handles have been closed. If you close those before launching your async process via system 1, ..., then it will not cause the server to block. You can also close them (immediately) within the async script or process.

    With respect to Win32::Process, if you set the iflag parameter to false:

    Win32::Process::Create($obj,$appname,$cmdline,$iflags,$cflags,$curdir)

Creates a new process.
    Args:

        $obj            container for process object
        $appname        full path name of executable module
        $cmdline        command line args
        $iflags         flag: inherit calling processes handles or not
        $cflags         flags for creation (see exported vars below)
        $curdir         working dir of new process

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    That will also prevent the problem.

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      If you close those before launching your async process via system 1, ..., then it will not cause the server to block.

      :) yes, I'm aware that is common, and I had close ... and it didn't work

[reply]
        I had close ... and it didn't work

        Hm. Try: 

        use POSIX qw[ close ];

...
POSIX::close( $_ ) for 0 .. 255;

        [download]
        With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.
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