freebsd-dev/share/man/man7/style.perl.7

.\" Copyright (c) 2000 Josef Karthauser <joe@FreeBSD.org>
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.Dd October 16, 2000
.Dt STYLE.PERL 7
.Os FreeBSD
.Sh NAME
.Nm style.perl 7
.Nd "FreeBSD Perl source file style guide"
.Sh DESCRIPTION
This file specifies the preferred style for perl scripts in the
.Tn FreeBSD
source tree.
.Bd -literal -offset 0i
 #
 # Style guide for Perl.  Based on the kernel style guide.
 #

 #
 # VERY important single-line comments look like this.
 #

 # Most single-line comments look like this.

 # Multi-line comments look like this.  Make them real sentences.
 # Fill them so they look like real paragraphs.
.Ed
.Pp
All scripts should use the
.Fa strict
module and run without warnings. For example:
.Bd -literal -offset 0i
 #!/usr/bin/perl -w

 use strict;
 ...
.Ed
.Pp
Where possible run the script with taint mode switched on.  This
is documented in
.Xr perlsec 1 .
.Bd -literal -offset 0i
 #!/usr/bin/perl -wT
.Ed
.Pp
All variables should be defined before use; this is enforced if operating
under
.Fa use strict .
.Pp
Scope local variables should be defined using
.Fa my
.Va $variable
and not
.Fa local
.Va $variable .
The
.Fa local
declaration should only be used when it is required, and not by
default.  Lots of perl4 scripts use
.Fa local
because the
.Fa my
definition didn't exist prior to perl5.
.Bd -literal -offset 0i
 sub foo {
   my $var = shift;
   my @list = ();
   ...
 }
.Ed
.Pp
In most cases globals should be defined at the top of the code
using a
.Fa var
definition block:
.Bd -literal -offset 0i
 use vars qw($globalscalar @globalarray %globalhash);
.Ed
.Pp
In some cases it may be appropriate to use
.Fa my
.Va $variable =
.Li "value";
statements at the top of the script as an alternative to using
.Fa var
declarations.
.Pp
Whenever possible code should be run through the code checker
.Nm perl
.Ar -wc
.Ar script.pl
or
.Nm perl
.Ar -wcT
.Ar script.pl
and produce no warnings.
.Pp
Indentation and block style should follow
.Xr style 9
where applicable.
.Pp
Where possible scripts should use standard modules instead of
rewriting the code inline.  It may be appropriate in some cases to
import a CPAN module into the base system to facilitate this.
.Pp
Use
.Fa chomp
instead of
.Fa chop
where appropriate.

.Sh SEE ALSO
.Xr perlsec 1 ,
.Xr style 9
.Sh HISTORY
This man page is largely based on the
.Xr style 9
man-page in
.Tn FreeBSD .