1Perl::Critic::Policy::IUPnseperurlt:OC:uoCtnrptiurttii:bc:u:Pt:rePodohliPibecirytl:T:wDIoonAcpruugmtOeOpnuettnap(tu3it)o:n:ProhibitTwoArgOpen(3)
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NAME

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

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

13       The three-argument form of "open" (introduced in Perl 5.6) prevents
14       subtle bugs that occur when the filename starts with funny characters
15       like '>' or '<'.  The IO::File module provides a nice object-oriented
16       interface to filehandles, which I think is more elegant anyway.
17
18         open( $fh, '>output.txt' );          # not ok
19         open( $fh, q{>}, 'output.txt' );     # ok
20
21         use IO::File;
22         my $fh = IO::File->new( 'output.txt', q{>} ); # even better!
23
24       It's also more explicitly clear to define the input mode of the file,
25       as in the difference between these two:
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27         open( $fh, 'foo.txt' );       # BAD: Reader must think what default mode is
28         open( $fh, '<', 'foo.txt' );  # GOOD: Reader can see open mode
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30       There is also a one-argument form of "open" which retrieves the
31       expression to open from the global variable with the same name as the
32       handle, but this has the same problems as the two-argument form, and
33       adds in more ambiguity.
34
35         our $FH = '<foo.txt';
36         open( FH ); # not ok
37
38       This policy will not complain if the file explicitly states that it is
39       compatible with a version of perl prior to 5.6 via an include
40       statement, e.g. by having "require 5.005" in it.
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CONFIGURATION

43       This Policy is not configurable except for the standard options.
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NOTES

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

50       IO::Handle
51
52       IO::File
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AUTHOR

55       Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>
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58       Copyright (c) 2005-2021 Imaginative Software Systems.  All rights
59       reserved.
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61       This program is free software; you can redistribute it and/or modify it
62       under the same terms as Perl itself.
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66perl v5.36.0          Perl::Critic2:0:2P3o-l0i3c-y0:5:InputOutput::ProhibitTwoArgOpen(3)
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