Life without CPAN

LIFE WITHOUT CPANReinventing the Wheel

Bob [email protected]

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 develophttp://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:

use 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 stuff?

We need to review that license...

Sometimes it is easier to buy software


Mix of licenses

“Most, though not all, modules on CPAN are licensedunder the GNU Public License (GPL) or the Artisticlicense”

– CPAN FAQ


GPL

The GNU Public License is anegative

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 inMETA.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 isalready approved

ActiveState Perl’s PPO

Linux package installer (yum, apt, etc.)


“This stuff is broken!”

Perl & CPAN have a strong culture of quality and testing... Butthere 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 Overflow

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 updatedall the timeA fix 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 find 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 withregular expressions

But in a pinch...

i f ( $ i n p u t =˜ qr { (< t i t l e >) ( . ∗ ) (</ t i t l e >) }x) {

$ t i t l e = $2 ;}


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)

use Date : : C a l c qw( Add Delta Days D a t e t o T e x tDay 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 ) {

$ d a y s u n t i l s u n d a y = 7 ;}f o r ( my $ i =0; $ i <8; $ i++ ) {

@date = Add Delta Days ( @date ,$ d a y s u n t i l s u n d a y ) ;

say D a t e t o T e x t ( @date ) ;$ d a y s u n t i l s u n d a y = 7 ;

}


The Next Eight Sundays (POSIX)

use POSIX qw( mktime s t r f t i m e ) ;use c o n s t a n t {

MDAY => 3 ,WDAY => 6 ,

} ;my @date = l o c a l t i m e ( t ime ( ) ) ;f o r (my $ i =0; $ i <8; $ i++) {

$date [MDAY] += 7 − $date [WDAY] ;@date = l o c a l t i m e ( mktime ( @date ) ) ;say s t r f t i m e ( ”%a %d−%b−%Y” , @date ) ;

}


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 {

my $command = s h i f t ;my $ p i d = f o r k ( ) ;i f ( $ p i d ) {

push @ c h i l d r e n , $ p i d ;}e l s i f ( $ p i d == 0 ) {

system ( @{$command} ) ;e x i t 0 ;

}}


Fork continued

f o r ( my $ i =1; $ i <= 5 2 ; $ i++ ) {spawn command ( [ ” whateve r ” , $ i ] ) ;

}

f o r e a c h my $ p i d ( @ c h i l d r e n ) {w a i t p i d ( $pid , 0 ) ;

}


Core Modules

Don’t forget the core modules!

Benchmark

Carp

Cwd

Data::Dumper

File::stat

Getopt::Long

IO::Handle

IO::Socket

Log::Message

Math::BigInt

Memoize

Pod::Usage

POSIX

Test::More

Time::Local

682 altogether!


REMEMBER

“There are three great virtues of a programmer:laziness, impatience and hubris”

– Larry Wall

Be lazy and impatient – use CPAN!


Life without CPAN

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