Perl debugger tips and tricks

In the debugger:

• $DB::deep = 500 # prevent the warning "100 levels deep in subroutine calls!"
• {{v # display the code ahead after every step
• b Test::Something::App::Module::login # break at a particular subroutine in a specified module
• c # continue until the next breakpoint

Also remember that the debugger often provides extra stack trace information for 'untraceable' warnings or errors.

Ruby basics

• Install Ruby
• Setup gems
• gem install nokogiri
• gem install builder
• Database: SQLite (docs)
• Database driver:
• ! gem install dbi (docs don't work, but these docs do)
• ! gem install dbd-sqlite3

• ? gem install sqlite-ruby (docs)

• Write script offline
• Host on Heroku

Save URL to a file

require 'open-uri'
open('image.png', 'wb') do |file|
    file << open('http://example.com/image.png').read
end

is this the same as:

require 'open-uri'
file = open('image.png', 'wb')
file << open('http://example.com/image.png').read

Fetch URL through a proxy

print Net::HTTP::Proxy(proxy_addr, proxy_port, proxy_user, proxy_pass).get URI.parse('http://www.compufer.com/')

Hello world

puts "Hello, what's your name?"
STDOUT.flush
name = gets.chomp
puts 'Hello, ' + name + '.'

Blocks

def try  

  if block_given?  

    yield  

  else  

    puts "no block"  

  end  

end  

try # => "no block"  

try { puts "hello" } # => "hello"  

try do puts "hello" end # => "hello" 

Notes

• Whichever variables(s) you pass into the block, the method will fill them with something, depending on what its function is. e.g. "open" puts a file handle in there.
• List of file modes
• Hash, Hashes
• ---------------
• Builder tut1, tut2, tut3

• Read docs
• open-uri docs
• open returns an IO like object
• File
• Ruby blocks (closures)

Make apt-get and aptitude work through a proxy

1) sudo vi /etc/apt/apt.conf.d/70debconf
2) It should already have: DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt || true";};
3) Add this after what's there (no blank lines):
Acquire {
        http {
                Proxy "http://user:pass@host:port";
                No-Cache "false";
                Max-Age "86400";
                No-Store "false";
        };
};
Thanks

Handle the database with Test::Class

package My::Test;

use base 'Test::Class';

sub startup : Tests(startup => 1) {
    $schema = NAP::PRL::Schema->connect( $dsn, $user, $password );
}

sub setup : Test(setup) {
    $schema->txn_begin;
}

sub teardown : Test(teardown) {
    $schema->txn_rollback;
}

Which version of Ubuntu?

Which version of Ubuntu should I install?

• 11.04 - Yes! This works fine.
• 11.10 - No. The menus are borked.

These are all the lovely settings you're missing in >11.04:

System preferences:



System administration:



Control centre:

See alternative linux window managers.

Enable scrolling in GNU screen

.screenrc: 
termcapinfo xterm* ti@:te@ 

Thanks 

Install ruby gems

sudo yum -y install gcc ruby-devel rubygems
sudo gem install nokogiri

DBIx::Class basics

# SELECT COUNT(*) FROM product WHERE id = 104316
my $rs = $schema->resultset( 'Public::Product' )->search( { id => 104316 });
print "test: ".$rs->all;