Re^2: "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

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Re^3: "open" Best Practices
by marioroy (Prior) 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;
[download]

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
[download]

Regards, Mario

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