- vim and ruby scripts step by step

- introduction to regular expressions

- wget: download files from the command line

vim load_mediawiki_list.rb #Or use your favorite editor and create the file load_mediawiki_list.rb

<a> # pulse the “a” key (omit if you are using other editor)

$stdin.read.each{|line| puts "#{$1} => #{$2}" if line =~ /<li>([^:]*): (.*)/}

:wq # save and close in Vim

wget “http://wiki.favpal.org/Seekr_City/Abbreviations” -O – | ruby load_mediawiki_list.rb

We are going to use it a lot and three of the most common uses are the next ones:

wget http://www.gutenberg.org/dirs/etext95/study10.txt

The file is downloaded as saved as study10.txt We could define the file name with the option “-O”:

wget http://www.gutenberg.org/dirs/etext95/study10.txt -O book.txt

Or you also could send it to the standard output with “-O -” and use a pipe (|):

wget http://www.gutenberg.org/dirs/etext95/study10.txt -O – | grep Holmes

Open a terminal and:

wget http://www.gutenberg.org/dirs/etext95/study10.txt

irb

book=IO.read("study10.txt")

i = book=~/Watson/
=> 15078
book[i-50..i+10]
=> "m.\r\n\r\n\"Whatever have you been doing with yourself, Watson?\"\r\n"

i = book=~/\sWatson\s/
=> 15078
book[i-50..i+10]
=> "click\r\nof the latch as she opened it.\r\n\r\n\"Does Dr. Watson liv"

i = book=~/(\w*) Street/
=> Baker
book[i-50..i+10]
=> "his\r\nrooms with me.  \"I have my eye on a suite in Baker Stree"

a=[]
book.each{|line| a<
	<line if line=~/(\w*) Street/}
=> ...

a.size
=> 9

puts a
=> rooms with me.  "I have my eye on a suite in <strong>Baker Street</strong>,"
at No. 221B, {5} <strong>Baker Street</strong>, of which he had spoken at our
and we stood together at the corner of <strong>Henrietta Street</strong> a-talkin'.
...

The following examples illustrate a few specifications that could be expressed in a regular expression:

* the sequence of characters “car” in any context, such as “car”, “cartoon”, or “bicarbonate”
* the word “car” when it appears as an isolated word
* the word “car” when preceded by the word “blue” or “red”
* a dollar sign immediately followed by one or more digits, and then optionally a period and exactly two more digits

Regular expressions can be much more complex than these examples.” (from Wikipedia)

Now, open a terminal, introduce “irb” or go to tryruby and continue playing:

1. "My child loves cartoons and dogs"=~/car/
=> 14

# \s: whitespace
"My child loves cartoons and dogs"=~/[\s]car[\s]/
=> nil

"My child loves cars and dogs"=~/[\s]cars[\s]/
=> 14

"My child loves cars! and dogs"=~/[\s]cars[\s]/
=> nil

# \w: any word character
# [^\w]: any character except word characters
"My child loves cars!"=~/[^\w]cars[^\w]/
=> 14

"My child loves cars"=~/[^\w]cars[^\w]/
=> nil

#$ end of the string
"My child loves cars"=~/[^\w]cars$/
=> 14

#([^\w]|$) any non word character or end of the string
"My child loves cars"=~/[^\w]cars([^\w]|$)/
=> 14

"My child loves blue cars"=~/blue cars/
=> 15

"My child loves red cars"=~/(blue|red) cars/

=> 15
$1
=> red

"My child loves blue cars"=~/(blue|red) cars/
=> 15
$1
=> blue

More info here:

]]> http://railscity.wordpress.com/2008/06/22/introduction-to-regular-expressions/feed/ 2 hecpeare http://railscity.wordpress.com/2008/06/20/yaml/ http://railscity.wordpress.com/2008/06/20/yaml/#comments Fri, 20 Jun 2008 17:01:31 +0000 Héctor http://railscity.wordpress.com/?p=18 ]]>

require 'yaml'
=> true

any_object=[2,3,"hi"]
=> [2, 3, "hi"]

dumped=YAML.dump(any_object) # You could store it in a file
=> "--- \n- 2\n- 3\n- hi\n"

YAML.load(dumped)
=> [2, 3, "hi"]

irb

File.open("file.txt","w"){|f| f.puts "override with this"}
=> nil
IO.read("file.txt")
=> "override with this\n"

File.open("file.txt","w"){|f| f.puts "override with this 2"}
=> nil
IO.read("file.txt")
=> "override with this 2\n"

File.open("file.txt","a"){|f| f.puts "add this"}
=> nil
text=IO.read("file.txt")
=> "override with this 2\nadd this\n"

puts text
> override with this
> add this
=> nil

“string #{2*5}”
> “string 10″

exit

vim each_args.rb
<a>

$*.each{|n| puts n}

<Esc>
:wq

ruby each_args.rb argument1 argument2
> argument1
> argument2

In Ubuntu, install the convert package:
sudo aptitude install convert

vim reduce_image.rb
<a>

$*.each{|file| system("convert #{file} -resize 50% #{file}")}

<Esc>
:wq

wget http://upload.wikimedia.org/wikipedia/commons/9/97/The_Earth_seen_from_Apollo_17.jpg -O Earth.jpg
wget http://upload.wikimedia.org/wikipedia/commons/d/dd/Full_Moon_Luc_Viatour.jpg -O Moon.jpg

ls -l *jpg
> -rw-r–r– 1 hector hector 6511067 2005-07-31 04:25 Earth.jpg
> -rw-r–r– 1 hector hector  924214 2006-10-07 23:59 Moon.jpg

ruby reduce_image.rb *jpg
ls -l *jpg
> -rw-r–r– 1 hector hector 2521991 2008-06-14 23:14 Earth.jpg
> -rw-r–r– 1 hector hector  246682 2008-06-14 23:14 Moon.jpg

ruby reduce_image.rb *jpg
ls -l *jpg
> -rw-r–r– 1 hector hector 689873 2008-06-14 23:15 Earth.jpg
> -rw-r–r– 1 hector hector  71721 2008-06-14 23:15 Moon.jpg

irb

a=Time.now.month
=> 6

"June" if a==6
=> "June"

"not January" unless a==1
=> nil

if Time.now.year==2008
  out="ok"
else
  out="really?"
end
=> "ok"

# And other shorter way:
out = Time.now.year==2008 ? "ok" : "really?"
=> "ok"

Open a terminal and follow this great article (but keep in mind that the Slicehost articles are for servers):

sudo aptitude install ruby1.8-dev ruby1.8 ri1.8 rdoc1.8 irb1.8 libreadline-ruby1.8 libruby1.8 libopenssl-ruby sqlite3 libsqlite3-ruby1.8

sudo ln -s /usr/bin/ruby1.8 /usr/bin/ruby

sudo ln -s /usr/bin/ri1.8 /usr/bin/ri

sudo ln -s /usr/bin/rdoc1.8 /usr/bin/rdoc

sudo ln -s /usr/bin/irb1.8 /usr/bin/irb

mkdir ~/sources

cd ~/sources

wget http://rubyforge.org/frs/download.php/34638/rubygems-1.1.0.tgz

tar xzvf rubygems-1.1.0.tgz

cd  rubygems-1.1.0

sudo ruby setup.rb

sudo ln -s /usr/bin/gem1.8 /usr/bin/gem

sudo ln -s /usr/bin/gem1.8 /usr/bin/gem

sudo gem update --system

sudo gem install rails

sudo aptitude install postfix subversion