Life without CPAN

LIFE WITHOUT CPAN
Reinventing the Wheel
Bob Ernst
BobErnstStl@gmail.com
ST. LOUIS PERL MONGERS
July 17, 2013
Bob Ernst Life Without CPAN

Comprehensive Perl Archive Network
http://www.cpan.org/
22,938 Perl modules (and growing!)
10,781 authors (and growing!)
Possibly the best feature of Perl
... and sometimes you can't use it

$677 Million
In 2004, CPAN had 15.4 million lines of code, which would cost
$677,000,000 to develop
http://developers.slashdot.org/story/04/07/30/1229239/cpan-677-million-of-perl

Handy tools
cpan
cpanm
cpanp
perlbrew

Why don't people use CPAN?
And how did I become one of them??

But I don't have root..."
No root access? That is an easy one:
us e l o c a l : : l i b ;

Why is this so complicated?"
CPAN often has objected-oriented Perl
Embarrassment of riches
More & Better module documentation couldn't hurt

I don't have enough disk space..."
Who doesn't have lots of disk space in 2013?
SSD drives - fast, but small
Raspberry Pi
Embedded systems
Shared hosting
Virtual Machines
Disk quotas

NIH - Not Invented Here
Pretty silly, but unfortunately common

Security Concerns
Some organizations are serious about security
What company wrote this software?
You want to connect to the internet??

Local Mirror & Packing
CPAN::Mini
CPAN::Mini::Inject
Pinto
Carton

Licensing
What is this FOSS / open source / shareware / freeware stu?
We need to review that license...
Sometimes it is easier to buy software

Mix of licenses
Most, though not all, modules on CPAN are licensed
under the GNU Public License (GPL) or the Artistic
license
{ CPAN FAQ

GPL
The GNU Public License is a
negative
in some organizations

CPAN::Meta::Spec
agpl_3 GNU Affero General Public License, Version 3
apache_1_1 Apache Software License, Version 1.1
apache_2_0 Apache License, Version 2.0
artistic_1 Artistic License, (Version 1)
artistic_2 Artistic License, Version 2.0
bsd BSD License (three-clause)
freebsd FreeBSD License (two-clause)
gfdl_1_2 GNU Free Documentation License, Version 1.2
gfdl_1_3 GNU Free Documentation License, Version 1.3
gpl_1 GNU General Public License, Version 1
lgpl_2_1 GNU Lesser General Public License, Version 2.1
lgpl_3_0 GNU Lesser General Public License, Version 3.0
mit MIT (aka X11) License
mozilla_1_0 Mozilla Public License, Version 1.0
mozilla_1_1 Mozilla Public License, Version 1.1
openssl OpenSSL License
perl_5 The Perl 5 License (Artistic 1 GPL 1 or later)
qpl_1_0 Q Public License, Version 1.0
ssleay Original SSLeay License
sun Sun Internet Standards Source License (SISSL)
zlib zlib License

And...
open_source Other Open Source Initiative (OSI) approved license
restricted Requires special permission from copyright holder
unrestricted Not an OSI approved license, but not restricted
unknown License not provided in metadata
May be hard to get approval!

Missing licenses
16.6% of CPAN uploads this year don't have a license in
META.yml
(Older modules are worse!)
http://cpants.cpanauthors.org/kwalitee/metayml has license

Get the modules without CPAN
Perhaps you have access to another source of modules that is
already approved
ActiveState Perl's PPO
Linux package installer (yum, apt, etc.)

This stu is broken!
Perl CPAN have a strong culture of quality and testing... But
there are buggy modules
Look for recommended modules
http://cpanratings.perl.org/
Check outstanding bug list for modules
Report the bug!
Fix the bug yourself (and share the patch)
Fork the module

Who am I going to call for support?
Submit a bug report
IRC
Perl Monks
Stack Over
ow
Mailing lists
ActiveState

Deploying to Production
No internet access (in secure environments)
Slow installs
Missing dependencies
Broken installs

Building on Quicksand
CPAN modules typically have dependencies, modules are updated
all the time
A

x in one module might break the module you are counting on!

Make it solid
perlbrew to get the right version of Perl
CPAN::Mini to get the right version of everything else

You've fought the political battle and lost...
What do you do?

Reinvent the Wheel

You aren't alone
If you google XYZ Perl, you'll

nd a lot of questions like:
How do I XYZ in Perl without using CPAN?

XML Parsing
Writing an XML parser is hard work
XML isn't a regular language so it can't be parsed with
regular expressions
But in a pinch...
i f ( $ i n p u t =~ qr f ( t i t l e ) ( . ) (/ t i t l e ) gx
) f
$ t i t l e = $2 ;
g

Date and Time
Date::Manip and Date::Calc are so powerful...
what to do when they aren't available?

The Next Eight Sundays (Date::Calc)
us e Date : : Cal c qw( Add De l ta Days Da t e t o Te x t
Day of Week Today ) ;
my @date = Today ( ) ;
my $ d a y s u n t i l s u n d a y = 7 Day of Week ( @date
) ;
i f ( $ d a y s u n t i l s u n d a y == 0 ) f
$ d a y s u n t i l s u n d a y = 7 ;
g
f o r ( my $ i =0; $i 8; $ i++ ) f
@date = Add De l ta Days ( @date ,
$ d a y s u n t i l s u n d a y ) ;
say Da t e t o Te x t ( @date ) ;
$ d a y s u n t i l s u n d a y = 7 ;
g

The Next Eight Sundays (POSIX)
us e POSIX qw( mktime s t r f t ime ) ;
us e c o n s t a n t f
MDAY = 3 ,
WDAY = 6 ,
g ;
my @date = l o c a l t ime ( t ime ( ) ) ;
f o r (my $ i =0; $i 8; $ i++) f
$dat e [MDAY] += 7 $dat e [WDAY] ;
@date = l o c a l t ime ( mktime ( @date ) ) ;
say s t r f t ime ( %a %d%b%Y , @date ) ;
g

Parallel Processing
Modules like Parallel::Queue are great...
if you have CPAN.

Old Fashion Fork
our @c h i l d r e n = ( ) ;
sub spawn command f
my $command = s h i f t ;
my $pid = f o r k ( ) ;
i f ( $pid ) f
push @c h i l d r e n , $pid ;
g
e l s i f ( $pid == 0 ) f
sys tem ( @f$commandg ) ;
e x i t 0 ;
g
g

Fork continued
f o r ( my $ i =1; $ i = 5 2 ; $ i++ ) f
spawn command ( [ what e v e r , $ i ] ) ;
g
f o r e a c h my $pid ( @c h i l d r e n ) f
wa i t p i d ( $pid , 0 ) ;
g

Life without CPAN

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