01-30-2017
Lets not get deep into subshells.
I'm sure you experts don't have too many nested subshells in your code
In my opinion, it lowers the control you have in your program.
So if you have small, efficient script with no nested subshells, are backquotes still the lowest denominator e.g will it run without magic cookie on any unix OS ever produced ?
Example would be a simple mv script using basename command in subshell.
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Hi,
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Input file:
'data_1'
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LEARN ABOUT CENTOS
perl::critic::policy::inputoutput::prohibitbacktickoperators
Perl::Critic::Policy::InputOutput::ProhibitBacktickOperaUser(Contributed Perl DocumPerl::Critic::Policy::InputOutput::ProhibitBacktickOperators(3)
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 v5.16.3 2014-06-09 Perl::Critic::Policy::InputOutput::ProhibitBacktickOperators(3)