Regex or Regular Expressions are not as hard as they look once you understand what the special characters mean. If you learn these 11 regex special characters you can understand any regex out there.
| Character | Meaning | Example |
|---|---|---|
| * | Match zero, one or more of the previous | Ah* matches "Ahhhhh" or "A" |
| ? | Match zero or one of the previous | Ah? matches "Al" or "Ah"
|
| + | Match one or more of the previous | Ah+ matches "Ah" or "Ahhh" but not "A" |
| \ | Used to escape a special character | Hungry\? matches "Hungry?" |
| . | Wildcard character, matches any character | do.* matches "dog", "door", "dot", etc. |
| ( ) | Group characters | See example for | |
| [ ] | Matches a range of characters |
[cbf]ar matches "car", "bar", or "far"[0-9]+ matches any positive integer
[a-zA-Z] matches ascii letters a-z (uppercase and lower case)[^0-9] matches any character not 0-9.
|
| | | Matche previous OR next character/group | (Mon|Tues)day matches "Monday" or "Tuesday" |
| { } | Matches a specified number of occurrences of the previous |
[0-9]{3} matches "315" but not "31"[0-9]{2,4} matches "12", "123", and "1234"[0-9]{2,} matches "1234567..."
|
| ^ | Beginning of a string. Or within a character range [] negation. |
^http matches strings that begin with http, such as a url.[^0-9] matches any character not 0-9. |
| $ | End of a string. | ing$ matches "exciting" but not "ingenious" |