• NAME
• DESCRIPTION
• NOTES
• AUTHOR
• COPYRIGHT

NAME

Perl::Critic::Policy::InputOutput::ProhibitBacktickOperators

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

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 the perlipc manpage for more discussion on using wait() instead of $SIG{CHLD} = 'IGNORE'.

AUTHOR

Jeffrey Ryan Thalhammer <thaljef@cpan.org>

COPYRIGHT

Copyright (c) 2005-2007 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.