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Re^2: "open" Best Practices

by karlgoethebier (Monsignor)
on Jul 12, 2019 at 13:30 UTC ( #11102730=note: print w/replies, xml ) Need Help??


in reply to Re: "open" Best Practices
in thread "open" Best Practices

"...the easy part."

Well said. Some callow thoughts about some situations when things get a little bit harder: I just wondered if some ugly locking stuff could be handled with mce_open from MCE::Shared::Handle. Probably this may be yet another case of total abuse of a module. And testing with lsof if a file is in use might be an option from time to time as well. Best regards, Karl

«The Crux of the Biscuit is the Apostrophe»

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Re^3: "open" Best Practices
by marioroy (Vicar) on Jul 14, 2019 at 16:39 UTC

    Hi karlgoethebier,

    The mce_open call behaves similarly to the native open in Perl. It creates a shared handle with exclusive locking handled transparently.

    Example:

    use strict; use warnings; use feature 'say'; use MCE::Hobo; use MCE::Shared; # Passing a file ref without IO::FDPass will work for \*STDIN, # \*STDOUT, \*STDERR, and \*main::DATA only. Otherwise, providing # the actual path is preferred (i.e. "/path/to/file"). mce_open my $out, '>>', \*STDOUT or die 'open failed: $!'; mce_open my $err, '>>', \*STDERR or die 'open failed: $!'; printf $out "shared fileno(\$out) is %d\n", fileno($out); printf $out "shared fileno(\$err) is %d\n", fileno($err); if ($^O ne 'MSWin32') { mce_open my $log, '>>', '/dev/null' or die 'open failed: $!'; say $log "Hello, there!"; # sent to null } # The shared-handles work with threads, MCE::Hobo, MCE::Child, # Parallel::ForkManager, and other parallel modules on CPAN. # Note: There is no reason to choose MCE::Child over MCE::Hobo # if already involving the shared-manager. sub foo { my ($id) = @_; say $out "Hello, from pid $$"; } MCE::Hobo->create('foo', $_) for 1..4; MCE::Hobo->wait_all;

    Output:

    shared fileno($out) is 1 shared fileno($err) is 2 Hello, from pid 4651 Hello, from pid 4652 Hello, from pid 4653 Hello, from pid 4654

    See also:

    https://metacpan.org/pod/MCE::Shared#DBM-SHARING
    https://metacpan.org/pod/MCE::Shared#LOGGER-DEMONSTRATION

    Regards, Mario

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