Regular Expressions
Useful site for writing and testing regex
- https://www.regexpal.com/
- https://regex101.com/
- http://regextutorials.com/index.html
- https://regexper.com/#%5E%28%5Ba-z%5D%2B%5Cd*_%5Ba-z%5Cd_%5D*%7C_%2B%5Ba-z%5Cd%5D%2B%5Ba-z%5Cd_%5D*%29%24
Image Source: https://twitter.com/manekinekko/status/1335330878403260419
| code | Purpose |
|---|---|
\d | represent any digit 0-9 |
[0-9] or [abc] | matches a range or any specfic item in the brackets could find a,b, or c but will find all of them |
\D | match any NON-digit characters |
[^0-9] or [^\d] | says match all BUT these in which case this is digits |
\w | will match words, \D will match white space, punctuation, hyphens, etc. while \w does not. \w matches only letters and numbers, equivalently: [a-zA-Z0-9] |
\W | to match a non word character. matches opposite of alphanumeric and is equivalent to [^_a-zA-Z0-9] |
\s | match a space character |
\n | New line |
\t | a tab |
\r | carriage return |
. | match any single character |
\b | boundry, so for a word \bA.{5}T\b the boundries encompass words that start with 'A', end with 'T' and have 5 characters in the middle like ANCYENT or ANCIENT also akin to \b\w{7}\b |
^ | beginning of a line anchor |
$ | end of a line anchor |
| the pipe is an 'or' statement in brackets is saying 't' OR 'T' in a regex search | |
[0-3[4-5]] | Union of 2 character sets, this would return 04, 05, 14, 15, 24, 25, 34, 35, this can also work with negation to use a set of 'NOT THESE' characters |
| Quantifier | Description | |
|---|---|---|
{8} | quantifyer, same as linux CLI .{8} would match any 8 characters, this one matches the patter a specific number of times, 8 times. | |
{8,} | the comma means it will match or more occurances of the pattern | |
{2,4} | will match the pattern anytime it ocurs 2-4 times any of those options are captured |
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