Perl::Critic::PPerl::Critic::Policy::InputOutput::ProhibitBacktickOperators(3)NAMEPerl::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 v5.14.1 Perl::Critic::Policy::InputOutput::ProhibitBacktickOperators(3)
