.\" Automatically generated by Pod::Man 4.14 (Pod::Simple 3.40)
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" Set up some character translations and predefined strings.  \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote.  \*(C+ will
.\" give a nicer C++.  Capital omega is used to do unbreakable dashes and
.\" therefore won't be available.  \*(C` and \*(C' expand to `' in nroff,
.\" nothing in troff, for use with C<>.
.tr \(*W-
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
.    ds -- \(*W-
.    ds PI pi
.    if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.    if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\"  diablo 12 pitch
.    ds L" ""
.    ds R" ""
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds -- \|\(em\|
.    ds PI \(*p
.    ds L" ``
.    ds R" ''
.    ds C`
.    ds C'
'br\}
.\"
.\" Escape single quotes in literal strings from groff's Unicode transform.
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\"
.\" If the F register is >0, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.\"
.\" Avoid warning from groff about undefined register 'F'.
.de IX
..
.nr rF 0
.if \n(.g .if rF .nr rF 1
.if (\n(rF:(\n(.g==0)) \{\
.    if \nF \{\
.        de IX
.        tm Index:\\$1\t\\n%\t"\\$2"
..
.        if !\nF==2 \{\
.            nr % 0
.            nr F 2
.        \}
.    \}
.\}
.rr rF
.\" ========================================================================
.\"
.IX Title "Perl::Critic::Policy::Compatibility::ProhibitUnixDevNull 3pm"
.TH Perl::Critic::Policy::Compatibility::ProhibitUnixDevNull 3pm "2021-02-28" "perl v5.32.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Perl::Critic::Policy::Compatibility::ProhibitUnixDevNull \- don't use explicit /dev/null
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This policy is part of the \f(CW\*(C`Perl::Critic::Pulp\*(C'\fR
add-on.  It ask you to not to use filename
.Sp
.RS 4
\&\fI/dev/null\fR
.RE
.PP
explicitly, but instead \f(CW\*(C`File::Spec\->devnull()\*(C'\fR for maximum portability
across operating systems.
.PP
This policy is under the \f(CW\*(C`maintenance\*(C'\fR theme (see
\&\*(L"\s-1POLICY THEMES\*(R"\s0 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.
.PP
\&\f(CW\*(C`devnull()\*(C'\fR is new in \f(CW\*(C`File::Spec\*(C'\fR version 0.8, so you should require that
version (it's included in Perl 5.6.0 and up).
.PP
The checks for \fI/dev/null\fR are unsophisticated.  A violation is reported
for any string \f(CW\*(C`/dev/null\*(C'\fR, possibly with an \f(CW\*(C`open\*(C'\fR style mode part, and
any \f(CW\*(C`qw\*(C'\fR containing \f(CW\*(C`/dev/null\*(C'\fR.
.PP
.Vb 3
\&    open my $fh, \*(Aq< /dev/null\*(Aq;                    # bad
\&    do_something ("/dev/null");                    # bad
\&    foreach my $file (qw(/dev/null /etc/passwd))   # bad
.Ve
.PP
String comparisons are allowed because they're not uses of \fI/dev/null\fR as
such but likely some sort of cross-platform check.
.PP
.Vb 2
\&    if ($f eq \*(Aq/dev/null\*(Aq) { ... }                 # ok
\&    return ($f ne \*(Aq>/dev/null\*(Aq);                   # ok
.Ve
.PP
\&\fI/dev/null\fR as just part of a string is allowed, including things like
backticks and \f(CW\*(C`system\*(C'\fR.
.PP
.Vb 3
\&    print "Flames to /dev/null please\en"           # ok
\&    system (\*(Aqrmdir /foo/bar >/dev/null 2>&1\*(Aq);     # ok
\&    $hi = \`echo hi </dev/null\`;                    # ok
.Ve
.PP
Whether \fI/dev/null\fR 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.
.SS "Disabling"
.IX Subsection "Disabling"
If you only ever use a system with \fI/dev/null\fR or if everything else you
write is hopelessly wedded to Unix anyway then you can disable
\&\f(CW\*(C`ProhibitUnixDevNull\*(C'\fR from your \fI.perlcriticrc\fR in the usual way (see
\&\*(L"\s-1CONFIGURATION\*(R"\s0 in Perl::Critic),
.PP
.Vb 1
\&    [\-Compatibility::ProhibitUnixDevNull]
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Perl::Critic::Pulp, Perl::Critic, File::Spec
.SH "HOME PAGE"
.IX Header "HOME PAGE"
<http://user42.tuxfamily.org/perl\-critic\-pulp/index.html>
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2019, 2021 Kevin Ryde
.PP
Perl-Critic-Pulp is free software; you can redistribute it and/or modify it
under the terms of the \s-1GNU\s0 General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
.PP
Perl-Critic-Pulp is distributed in the hope that it will be useful, but
\&\s-1WITHOUT ANY WARRANTY\s0; without even the implied warranty of \s-1MERCHANTABILITY\s0
or \s-1FITNESS FOR A PARTICULAR PURPOSE.\s0  See the \s-1GNU\s0 General Public License for
more details.
.PP
You should have received a copy of the \s-1GNU\s0 General Public License along with
Perl-Critic-Pulp.  If not, see <http://www.gnu.org/licenses/>.