Perl: How to check if there is something being piped in

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perl::critic::policy::inputoutput::prohibitexplicitstdin

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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