Perl::Critic::Policy::InputOutput::ProhibitTwoArgOpen(3pm)
                                           User Contributed Perl Documentation


NAME
       Perl::Critic::Policy::InputOutput::ProhibitTwoArgOpen - Write "open
       $fh, q{<}, $filename;" instead of "open $fh, "<$filename";".

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

DESCRIPTION
       The three-argument form of "open" (introduced in Perl 5.6) prevents
       subtle bugs that occur when the filename starts with funny characters
       like '>' or '<'.  The IO::File module provides a nice object-oriented
       interface to filehandles, which I think is more elegant anyway.

         open( $fh, '>output.txt' );          # not ok
         open( $fh, q{>}, 'output.txt' );     # ok

         use IO::File;
         my $fh = IO::File->new( 'output.txt', q{>} ); # even better!

       It's also more explicitly clear to define the input mode of the file,
       as in the difference between these two:

         open( $fh, 'foo.txt' );       # BAD: Reader must think what default mode is
         open( $fh, '<', 'foo.txt' );  # GOOD: Reader can see open mode

       There is also a one-argument form of "open" which retrieves the
       expression to open from the global variable with the same name as the
       handle, but this has the same problems as the two-argument form, and
       adds in more ambiguity.

         our $FH = '<foo.txt';
         open( FH ); # not ok

       This policy will not complain if the file explicitly states that it is
       compatible with a version of perl prior to 5.6 via an include
       statement, e.g. by having "require 5.005" in it.

CONFIGURATION
       This Policy is not configurable except for the standard options.

NOTES
       There is one case in which you are forced to use the two-argument form
       of open: when doing a safe pipe open, as described in perlipc.

SEE ALSO
       IO::Handle

       IO::File

AUTHOR
       Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>

COPYRIGHT
       Copyright (c) 2005-2021 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.

perl v5.38.0                      2023-07-26
                    Perl::Critic::Policy::InputOutput::ProhibitTwoArgOpen(3pm)