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.IX Title "Perl::Critic::Policy::InputOutput::ProhibitExplicitStdin 3pm"
.TH Perl::Critic::Policy::InputOutput::ProhibitExplicitStdin 3pm 2023-07-26 "perl v5.38.0" "User Contributed Perl Documentation"
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.SH NAME
Perl::Critic::Policy::InputOutput::ProhibitExplicitStdin \- Use "<>" or "<ARGV>" or a prompting module instead of "<STDIN>".
.SH AFFILIATION
.IX Header "AFFILIATION"
This Policy is part of the core Perl::Critic
distribution.
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Perl has a useful magic filehandle called \f(CW*ARGV\fR that checks the
command line and if there are any arguments, opens and reads those as
files.  If there are no arguments, \f(CW*ARGV\fR behaves like \f(CW*STDIN\fR
instead.  This behavior is almost always what you want if you want to
create a program that reads from \f(CW\*(C`STDIN\*(C'\fR.  This is often written in
one of the following two equivalent forms:
.PP
.Vb 7
\&  while (<ARGV>) {
\&    # ... do something with each input line ...
\&  }
\&  # or, equivalently:
\&  while (<>) {
\&    # ... do something with each input line ...
\&  }
.Ve
.PP
If you want to prompt for user input, try special purpose modules like
IO::Prompt.
.SH CONFIGURATION
.IX Header "CONFIGURATION"
This Policy is not configurable except for the standard options.
.SH CAVEATS
.IX Header "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
.PP
.Vb 1
\&  my $content = join \*(Aq\*(Aq, <STDIN>;
.Ve
.PP
because it interprets that line as the nonsensical statement:
.PP
.Vb 1
\&  my $content = join \*(Aq\*(Aq, < STDIN >;
.Ve
.PP
When that PPI bug is fixed, this policy should start catching those
violations automatically.
.SH CREDITS
.IX Header "CREDITS"
Initial development of this policy was supported by a grant from the
Perl Foundation.
.SH AUTHOR
.IX Header "AUTHOR"
Chris Dolan <cdolan@cpan.org>
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright (c) 2007\-2011 Chris Dolan.  Many rights reserved.
.PP
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