Regex Wildcards on steroids

Regular Expressions You’ve likely used the wildcard in windows search or coding (*), regular expressions take this to the next level * 10 (largest number I can think of). Useful tool for anyone not just developers. – Powerful search utility in most tools (Visual Studio, Word, Excel, …)

Literals Literal characters in regex are any character that you want to literally match. – “Google” in regex will match anything with “Google” in it regardless of what is before or after it. Will match “Googleplex” – “\bGoogle\b” in regex is stating that you want to match the whole word, solves the above mentioned problem.

Wildcards “*” means match this 0-infinite times “+” means match this 1-infinite times “.” mean match any character (except end of line) With the above you can see that “.*” would match anything and everything until it hits the first line break IE Windows:“\r\n” or UNIX:“\r”

Groups Groups allow you to create character groups. “[a-z]” will match any character that is a lowercase letter. “[0-9]” will match any digit. “[a-zA-Z]” will match any character that is lowercase or uppercase “[aZd3]” will match only the characters defined in the group “a”, “Z”, “d”, and “3”. “[^0-9]” will match anything that is not a number

Pop Quiz Write a regular expression to find a phone number matching the following pattern (xxx)xxx-xxxx \([0-9][0-9][0-9]\)[0-9][0-9][0-9]-[0-9][0-9][0- 9][0-9] – Why did we have to use “\(“ and “\)”? – A “\” is to escape a regex special character – A “(“ and “)” are special characters meaning capture to backreference (capturing group)

Capturing Groups These are handy for the replace section of Find and Replace. “(“ followed by a “)” creates a capturing group that is back referenced automatically by it’s index (non-zero) in the regex, some languages allow named capture groups. “(.*)” captures any character (except line break) and puts it into back reference 1.

DEMO Word Visual Studio Notepad++

Don’t go. crazy Be wary regular expressions are greedy by default. Example: – This is like hell this merchant just keeps wanting to sell...it's so frustrating – “.*?ell” non-greedy – “.*ell” greedy

Special Characters “\d” is any number or equivalent to “[0-9]” “\D” is the opposite of the above or equivalent to “[^0-9]” “\w” is any letter, number, or underscore or equivalent to “[0-9a-zA-Z_]” “\W” is the opposite of the above or equivalent to “[^0-9a-zA-Z_]” “\s” is any whitespace character (spaces, tabs, and linebreaks) “\S” is the opposite of the above

Optimizing It is always valuable to be as specific as possible since regex is greedy. “^” matches the beginning of string “$” matches the end of string “^\(\d\d\d\)\d\d\d-\d\d\d\d$” is perfect if the whole string is suppose to be a phone number and will be faster than “\(\d\d\d\)\d\d\d-\d\d\d\d”

Character Counts Specifying the number of times you want a thing to happen “\d{3}” will match 3 digits “\d{1,3}” will match 1 to 3 digits

Pop Quiz Q: Write a regular expression to find a phone number matching the following pattern (xxx)xxx-xxxx A: “\(\d{3}\)\d{3}-\d{3}”

DEMO Show how to code with Regex