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 v5.36.0                           Perl::Critic::Policy::InputOutput::ProhibitTwoArgOpen(3pm)