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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]
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 #{$1}\n" else print "no email\n" end if dets =~ /[A-Z]{1,2}\d{1,2}\s+\d[A-Z]{2,2}/ print "POSTCODE - address is #{$&}\n" else print "no postcode\n" end # 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 XYZ __END__ 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 -bash-3.2$ 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
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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.
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