Perl::Critic::Policy::Compatibility::ProhibitUnixDevNull3pm

Overview

This policy is part of the "Perl::Critic::Pulp" add-on. It ask you to not to use filename

explicitly, but instead "File::Spec->devnull()" for maximum portability across operating systems.

This policy is under the "maintenance" theme (see "POLICY THEMES" in Perl::Critic) on the basis that even if you're on a Unix system now you never know where your code might travel in the future.

"devnull()" is new in "File::Spec" version 0.8, so you should require that version (it's included in Perl 5.6.0 and up).

The checks for /dev/null are unsophisticated. A violation is reported for any string "/dev/null", possibly with an "open" style mode part, and any "qw" containing "/dev/null".

    open my $fh, '< /dev/null';                    # bad
    do_something ("/dev/null");                    # bad
    foreach my $file (qw(/dev/null /etc/passwd))   # bad

String comparisons are allowed because they're not uses of /dev/null as such but likely some sort of cross-platform check.

    if ($f eq '/dev/null') { ... }                 # ok
    return ($f ne '>/dev/null');                   # ok

/dev/null as just part of a string is allowed, including things like backticks and "system".

    print "Flames to /dev/null please\n"           # ok
    system ('rmdir /foo/bar >/dev/null 2>&1');     # ok
    $hi = `echo hi </dev/null`;                    # ok

Whether /dev/null is a good idea in such command strings depends what sort of shell you reach with that command and how much of Unix it might emulate on a non-Unix system.

    [-Compatibility::ProhibitUnixDevNull]

Home page

<http://user42.tuxfamily.org/perl-critic-pulp/index.html>