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perl::critic::policy::inputoutput::prohibitbacktickoperators(3pm) [debian man page]

Perl::Critic::Policy::InputOutput::ProhibitBacktickOperaUser(Contributed Perl DocPerl::Critic::Policy::InputOutput::ProhibitBacktickOperators(3pm)

NAME

       Perl::Critic::Policy::InputOutput::ProhibitBacktickOperators - Discourage stuff like "@files = `ls $directory`".

AFFILIATION

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

DESCRIPTION

       Backticks are super-convenient, especially for CGI programs, but I find that they make a lot of noise by filling up STDERR with messages
       when they fail.	I think its better to use IPC::Open3 to trap all the output and let the application decide what to do with it.

	   use IPC::Open3 'open3';
	   $SIG{CHLD} = 'IGNORE';

	   @output = `some_command`;			  #not ok

	   my ($writer, $reader, $err);
	   open3($writer, $reader, $err, 'some_command'); #ok;
	   @output = <$reader>;  #Output here
	   @errors = <$err>;	 #Errors here, instead of the console

CONFIGURATION

       Alternatively, if you do want to use backticks, you can restrict checks to void contexts by adding the following to your .perlcriticrc
       file:

	   [InputOutput::ProhibitBacktickOperators]
	   only_in_void_context = 1

       The purpose of backticks is to capture the output of an external command.  Use of them in a void context is likely a bug.  If the output
       isn't actually required, "system()" should be used.  Otherwise assign the result to a variable.

	   `some_command`;			#not ok
	   $output = `some_command`;		#ok
	   @output = `some_command`;		#ok

NOTES

       This policy also prohibits the generalized form of backticks seen as "qx{}".

       See perlipc for more discussion on using "wait()" instead of "$SIG{CHLD} = 'IGNORE'".

       You might consider using the "capture()" function from the IPC::System::Simple module for a safer way of doing what backticks do,
       especially on Windows.  The module also has a safe wrapper around "system()".

AUTHOR

       Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>

COPYRIGHT

       Copyright (c) 2005-2011 Imaginative Software Systems.  All 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 v5.14.2							    2012-06-07	 Perl::Critic::Policy::InputOutput::ProhibitBacktickOperators(3pm)

Check Out this Related Man Page

Perl::Critic::Policy::InputOutput::ProhibitTwoArgOpen(3pUser Contributed Perl DocumentatPerl::Critic::Policy::InputOutput::ProhibitTwoArgOpen(3pm)

NAME

       Perl::Critic::Policy::InputOutput::ProhibitTwoArgOpen - Write "open $fh, q{<}, $filename;" instead of "open $fh, "<$filename";".

AFFILIATION

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

DESCRIPTION

       The three-argument form of "open" (introduced in Perl 5.6) prevents subtle bugs that occur when the filename starts with funny characters
       like '>' or '<'.  The IO::File module provides a nice object-oriented interface to filehandles, which I think is more elegant anyway.

	 open( $fh, '>output.txt' );	      # not ok
	 open( $fh, q{>}, 'output.txt' );     # ok

	 use IO::File;
	 my $fh = IO::File->new( 'output.txt', q{>} ); # even better!

       It's also more explicitly clear to define the input mode of the file, as in the difference between these two:

	 open( $fh, 'foo.txt' );       # BAD: Reader must think what default mode is
	 open( $fh, '<', 'foo.txt' );  # GOOD: Reader can see open mode

       This policy will not complain if the file explicitly states that it is compatible with a version of perl prior to 5.6 via an include
       statement, e.g. by having "require 5.005" in it.

CONFIGURATION

       This Policy is not configurable except for the standard options.

NOTES

       There are two cases in which you are forced to use the two-argument form of open. When re-opening STDIN, STDOUT, or STDERR, and when doing
       a safe pipe open, as described in perlipc.

SEE ALSO

       IO::Handle

       IO::File

AUTHOR

       Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>

COPYRIGHT

       Copyright (c) 2005-2011 Imaginative Software Systems.  All rights reserved.

       This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perl v5.14.2							    2012-06-07		Perl::Critic::Policy::InputOutput::ProhibitTwoArgOpen(3pm)
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