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Regular Expression (including documenation)
Strings and Regular Expressions example from a Well House Consultants training course
More on Strings and Regular Expressions [link]

This example is described in the following article(s):
   • Regular Expressions in Ruby - [link]
   • Search and replace in Ruby - Ruby Regular Expressions - [link]

Source code: d4_8 Module: R109
# Regular Expression Example in Ruby

print "Please give me your contact details: "
dets = gets.chomp

# Looking for a PATTERN - also known as a regular expression

# A regular expressoion return true / false to say if it matched ..
# and IN ADDTIONS it sets other things like $& for the string that matched

if dets =~ /(\S+)@(\S+)/
        print "EMAIL - address is #{$&}\n"
        print "Domain name is #{$2} and user name is #{$1}\n"
        print "no email\n"

if dets =~ /[A-Z]{1,2}\d{1,2}\s+\d[A-Z]{2,2}/
        print "POSTCODE - address is #{$&}\n"
        print "no postcode\n"

# A here document can be a good way of adding a comment block!
about = <<"XYZ"

This is an example that looks for a regular expression that
matches an email address. We have started with a simple
definition of an email address:

        \S Non-space
        + One or more (of previous item)
        @ literally an @ character
        \S Non-space
        + One or more (of previous item)

Elements of a Ruby regular expression ...

1. Literals - match a character exactly - examples
        @ 4 A a \+ \\ \.

2. Character Groups - match a chracter from a list of options - examples
        [aeiou] [A-Z]
        [^aeiou] (A character which is NOT a lower case vowel)
        \s \d \w (space character, digit, word character)
        \S \D \W (non space, non digit, non word character)
        . (Any character at all!)

3. Counts - the number of times to match the PREVIOUS item - examples
        + One or more times
        * zero or more times
        ? 0 or 1 times
        {1,2} once or twice

4. Anchors - to say if it's at the start or end
        ^ starts with
        $ ends with

Thus ... [A-Z]{1,2}\d{1,2}\s+\d[A-Z]{2,2}
        One or two capital letters, one or two digits, space
                a digit, 2 capital letters
Is a regular expression for a postcode



Sample Output

-bash-3.2$ ruby d4_8
Please give me your contact details: I live at SN12 6QL
no email
POSTCODE - address is SN12 6QL
-bash-3.2$ ruby d4_8
Please give me your contact details: I work at SN12 7NY and you can email graham@wellho.net which also reaches me
EMAIL - address is graham@wellho.net
Domain name is wellho.net and user name is graham
POSTCODE - address is SN12 7NY

Learn about this subject
This module and example are covered on the following public courses:
 * Learning to program in Ruby
 * Ruby Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Ruby are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Strings and Regular Expressions" training module. You'll find a description of the topic and some other closely related examples on the "Strings and Regular Expressions" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
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