Ruby on Rails over the prompt


Ruby on rails ha sthree important commands: 
erb, ruby, and rails.

1. erb command

The "erb" command reproduces html tags and 
executes what it is between <= ... >.
Example:

<% word = "Regards," %>
<html>
<head></head><body>
<p><%= word %></p>
</body></html>

Save this file with an rb extention, as regards.rb.
Run this program under the prompt command-line like this:


C:\ruby\>erb regards.rb


The output is:


<html>
<head></head><body>
<p>Regards,</p>
</body></html>

1. ruby command

C:\>cd ruby
The current version:


C:\ruby>ruby -v
ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32]




Program directly on the command line using the -e option:


C:\ruby>ruby -e 'puts "Regards"'
Regards



Programs can be stored in files:



1. A simple string



C:\ruby>echo print 'All the best of luck ... '> examples/best.rb
C:\ruby>cd examples
C:\ruby\examples>best.rb
All the best of luck ...
C:\ruby\examples>cd ..
C:\ruby>






2. fibo.rb


# Program to find the fibobacci  of a positive number
# Save this as fibonacci.rb
def fibonacci(n)
  if (n == 0 || n == 1) 
  1
  else 
  fibonacci(n-1) + fibonacci(n-2)
  end
end

print fibonacci(ARGV[0].to_i) "\n"

Outputs:


C:\ruby\examples>fibonacci.rb  1
1

C:\ruby\examples>fibonacci.rb  12
233

C:\ruby\examples>fibonacci.rb  23
46368

C:\ruby\examples>






3.Invoking ruby with no arguments


C:\ruby>cd ..

C:\>ruby
puts "Regards,"
puts "All the best of luck .."
^D
Regards,
All the best of luck ..

C:\>
^D means Ctrl-D.



4. using evaluation eval.rb utility


The file eval.rb is stored in te directory:
C:\ruby\samples\RubySrc-1.8.6\sample

Issue the command:
C:\ruby>cd C:\ruby\samples\RubySrc-1.8.6\sample
Isuue the following:
C:\ruby\samples\RubySrc-1.8.6\sample>ruby eval.rb
We get ruby> prompt. tape: puts "Regards"
ruby> puts "Regards"
We get:
Regards
nil
quit this prompt:
ruby> exit

C:\ruby\samples\RubySrc-1.8.6\sample>
C:\ruby\samples\RubySrc-1.8.6\sample>ruby eval.rb




5. Strings


Some examples:


ruby> 1+2
3
ruby> "xyz"
"xyz"

ruby> 'xyz'
"xyz"

ruby> puts "x\ny\nz"
x
y
z
nil

ruby> puts 'x\ny\nz'
x\ny\nz
nil

ruby> '\n'
"\\n"

ruby> '\234'
"\\234"

ruby> "abcd #{2*22} xyz"
"abcd 44 xyz"




Concatenation:


ruby> "avail" + "able"
"available"

ruby> "avail" * 3
"availavailavail"




Boolean and equalities


ruby> "gold" == "gold"
true
ruby> "gold" == "diamond"
false
ruby>





Test the calsses:



ruby> @a=-8.7
-8.7
ruby> @a.class
Float
ruby> @a=123
123
ruby> @a.class
Fixnum
ruby> @a="gold mouth"
"gold mouth"
ruby> @a.class
String
ruby>