Using RegEx

Full RE2 syntax reference at > https://github.com/google/re2/wiki/Syntax
Go RegExp doc at > https://golang.org/pkg/regexp/
More about general concepts > http://www.regular-expressions.info​
Basic Regex
Basics of Regular Expressions
Match
Don't match
Match A or B
You can match a word by putting it between two brackets.
As example, this will only match the word "Dinosaur": (Dinosaur)
Using ?: after opening parenthesis of a capturing group creates a non-capturing group. Useful for example with template function reFindAllSubmatches.
This will not sub-match the words "red, blue, green": 
{{ reFindAllSubmatches `(?:color=)(red|blue|green)` "color=red beautiful" }} 
To clarify more - it will not show dateid, because it's a whole match:
{{ slice (index (reFindAllSubmatches `(?:dateid=)([0-9]{5})` "dateid=12345") 0) 1 }}
You may also want to catch multiple options, for that we use a "Vertical bar" or also known as a "Pipe" between linux users.
As example, this will match if either "Cat" or "Dog" is present: (Cat|Dog)
To match anything of any length, use .*.
Character classes
Words
Characters
Special Characters
To match a word, you put it between two brackets. 
Example: (Banana)
For matching characters there are multiple options:
Matching specific characters:
For matching a specific character, you put them in square brackets.
This will match A, B and C: ([abc])
This will match every character from A-z: ([A-z])
This will match every number: ([0-9])
Sometimes you have to use special characters but it may cause conflicts. In this case, you will have to use an escape character.
For example, this is a star that doesn't interfere with other matches \*.
Understanding Regex
If you still do not know what Regex are or want to know more. Check out the cheat sheet on the site below. 
What is a Regex (Regular Expression)?
Great tools for writing and testing Regex
https://regex-golang.appspot.com/
regex-golang.appspot.com
regex101: build, test, and debug regex
regex101
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Last modified 1yr ago