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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::ProhibitExplicitStdinUser)Contributed Perl DocumenPerl::Critic::Policy::InputOutput::ProhibitExplicitStdin(3pm)

NAME

       Perl::Critic::Policy::InputOutput::ProhibitExplicitStdin - Use "<>" or "<ARGV>" or a prompting module instead of "<STDIN>".

AFFILIATION

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

DESCRIPTION

       Perl has a useful magic filehandle called *ARGV that checks the command line and if there are any arguments, opens and reads those as
       files.  If there are no arguments, *ARGV behaves like *STDIN instead.  This behavior is almost always what you want if you want to create a
       program that reads from "STDIN".  This is often written in one of the following two equivalent forms:

	 while (<ARGV>) {
	   # ... do something with each input line ...
	 }
	 # or, equivalently:
	 while (<>) {
	   # ... do something with each input line ...
	 }

       If you want to prompt for user input, try special purpose modules like IO::Prompt.

CONFIGURATION

       This Policy is not configurable except for the standard options.

CAVEATS

       Due to a bug in the current version of PPI (v1.119_03) and earlier, the readline operator is often misinterpreted as less-than and greater-
       than operators after a comma.  Therefore, this policy misses important cases like

	 my $content = join '', <STDIN>;

       because it interprets that line as the nonsensical statement:

	 my $content = join '', < STDIN >;

       When that PPI bug is fixed, this policy should start catching those violations automatically.

CREDITS

       Initial development of this policy was supported by a grant from the Perl Foundation.

AUTHOR

       Chris Dolan <cdolan@cpan.org>

COPYRIGHT

       Copyright (c) 2007-2011 Chris Dolan.  Many 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::ProhibitExplicitStdin(3pm)
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