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Perl::Critic::Policy::InputOutput::ProhibitBacktickOperators(3pm) | User Contributed Perl Documentation | Perl::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.
2023-10-27 | perl v5.36.0 |