Useful regular expressions for Ruby

regular_expression_patterns.rb

# Useful regular expressions
# http://net.tutsplus.com/tutorials/other/8-regular-expressions-you-should-know/

# username
/^[a-z0-9_-]{3,16}$/

# password
/^[a-z0-9_-]{6,18}$/

# Hex value
/^#?([a-f0-9]{6}|[a-f0-9]{3})$/

# Slug
/^[a-z0-9-]+$/

# Email
/^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/ 

# URL
/^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$/ 

# IP Address
/^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/

# HTML Tag
/^<([a-z]+)([^<]+)*(?:>(.*)<\/\1>|\s+\/>)$/