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Perl::Critic::Policy::UserrContributedPPerlyDocumentatput::RequireBriefOpen(3)

NAME
       Perl::Critic::Policy::InputOutput::RequireBriefOpen - Close filehandles
       as soon as possible after opening them.

AFFILIATION
       This Policy is part of the core Perl::Critic distribution.

DESCRIPTION
       One way that production systems fail unexpectedly is by running out of
       filehandles.  Filehandles are a finite resource on every	operating
       system that I'm aware of, and running out of them is virtually
       impossible to recover from.  The	solution is to not run out in the
       first place.  What causes programs to run out of	filehandles?  Usually,
       it's leaks: you open a filehandle and forget to close it, or just wait
       a really	long time before closing it.

       This problem is rarely exposed by test systems, because the tests
       rarely run long enough or have enough load to hit the filehandle	limit.
       So, the best way	to avoid the problem is	1) always close	all
       filehandles that	you open and 2)	close them as soon as is practical.

       This policy takes note of calls to "open()" where there is no matching
       "close()" call within "N" lines of code.	 If you	really need to do a
       lot of processing on an open filehandle,	then you can move that
       processing to another method like this:

	   sub process_data_file {
	       my ($self, $filename) = @_;
	       open my $fh, '<', $filename
		   or croak 'Failed to read datafile ' .  $filename . '; ' . $OS_ERROR;
	       $self->_parse_input_data($fh);
	       close $fh;
	       return;
	   }
	   sub _parse_input_data {
	       my ($self, $fh) = @_;
	       while (my $line = <$fh>)	{
		   ...
	       }
	       return;
	   }

       As a special case, this policy also allows code to return the
       filehandle after	the "open" instead of closing it.  Just	like the
       close, however, that "return" has to be within the right	number of
       lines.  From there, you're on your own to figure	out whether the	code
       is promptly closing the filehandle.

       The STDIN, STDOUT, and STDERR handles are exempt	from this policy.

CONFIGURATION
       This policy allows "close()" invocations	to be up to "N"	lines after
       their corresponding "open()" calls, where "N" defaults to 9.  You can
       override	this to	set it to a different number with the "lines" setting.
       To do this, put entries in a .perlcriticrc file like this:

	 [InputOutput::RequireBriefOpen]
	 lines = 5

CAVEATS
   "IO::File->new"
       This policy only	looks for explicit "open" calls.  It does not detect
       calls to	"CORE::open" or	"IO::File->new"	or the like.

   Is it the right lexical?
       We don't	currently check	for redeclared filehandles.  So	the following
       code is false negative, for example, because the	outer scoped
       filehandle is not closed:

	   open	my $fh,	'<', $file1 or croak;
	   if (open my $fh, '<', $file2) {
	       print <$fh>;
	       close $fh;
	   }

       This is a contrived example, but	it isn't uncommon for people to	use
       $fh for the name	of the filehandle every	time.  Perhaps it's time to
       think of	better variable	names...

CREDITS
       Initial development of this policy was supported	by a grant from	the
       Perl Foundation.

AUTHOR
       Chris Dolan <cdolan@cpan.org>

COPYRIGHT
       Copyright (c) 2007-2011 Chris Dolan.  Many rights reserved.

       This program is free software; you can redistribute it and/or modify it
       under the same terms as Perl itself.  The full text of this license can
       be found	in the LICENSE file included with this module

perl v5.32.0		Perl::Critic::Policy::InputOutput::RequireBriefOpen(3)

NAME | AFFILIATION | DESCRIPTION | CONFIGURATION | CAVEATS | CREDITS | AUTHOR | COPYRIGHT

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