Perl::Critic::Policy::InputOutput::ProhibitBacktickOperators.3pm

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Version: 2010-09-08 (fedora - 01/12/10)

Section: 3 (Bibliothèques de fonctions)

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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 <thaljef@cpan.org> Copyright (c) 2005-2009 Jeffrey Ryan Thalhammer. 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.