Regex and not

1. What is the NOT operator in regex?
2. What does *$ mean in regex?
3. How do I negate a word in regex?
4. What are regex flags?
5. Who invented regex?
6. What does colon mean in regex?
7. How does regex replace work?
8. How do you use negative lookahead?
9. What is non capturing group in regular expression?
10. How do you denote special characters in regex?
11. Which regular expression operator means 1 or more of the character before it?
12. Which is regex function?
13. Can we use or in regex?

What is the NOT operator in regex?

When used inside [ and ] the ^ (caret) is the not operator. That will match any character except for a b or c .

What does *$ mean in regex?

*$ means - match, from beginning to end, any character that appears zero or more times. Basically, that means - match everything from start to end of the string. ... Feel free to use an online tool like https://regex101.com/ to test out regex patterns and strings.

How do I negate a word in regex?

The negative lookahead construct is the pair of parentheses, with the opening parenthesis followed by a question mark and an exclamation point. Inside the lookahead [is any regex pattern].

What are regex flags?

A regular expression consists of a pattern and optional flags: g , i , m , u , s , y . Without flags and special symbols (that we'll study later), the search by a regexp is the same as a substring search. The method str. match(regexp) looks for matches: all of them if there's g flag, otherwise, only the first one.

Who invented regex?

Regular expressions originated in 1951, when mathematician Stephen Cole Kleene described regular languages using his mathematical notation called regular events.

What does colon mean in regex?

Colon : is simply colon. It means nothing, except special cases like, for example, clustering without capturing (also known as a non-capturing group): (?:pattern) Also it can be used in character classes, for example: [[:upper:]] However, in your case colon is just a colon.

How does regex replace work?

Replace(String, String, String, RegexOptions, TimeSpan) In a specified input string, replaces all strings that match a specified regular expression with a specified replacement string. Additional parameters specify options that modify the matching operation and a time-out interval if no match is found.

How do you use negative lookahead?

The negative lookahead construct is the pair of parentheses, with the opening parenthesis followed by a question mark and an exclamation point. Inside the lookahead, we have the trivial regex u. Positive lookahead works just the same.

What is non capturing group in regular expression?

A non-capturing group has the first benefit, but doesn't have the overhead of the second. You can still say a non-capturing group is optional, for example. Say you want to match numeric text, but some numbers could be written as 1st, 2nd, 3rd, 4th,...

How do you denote special characters in regex?

The forward slash character is used to denote the boundaries of the regular expression: ? The backslash character ( \ ) is the escaping character. It can be used to denote an escaped character, a string, literal, or one of the set of supported special characters.

Which regular expression operator means 1 or more of the character before it?

In a regular expression, '+' is a postfix operator meaning "one or more", i.e., it has to match at least one occurrence of the pattern that comes before it. As you can see, the pattern '(.

Which is regex function?

A regular expression lets you perform pattern matching on strings of characters. The regular expression syntax allows you to precisely define the pattern used to match strings, giving you much greater control than wildcard matching used in the LIKE predicate.

Can we use or in regex?

“Or” in regular expressions `||` ... Fortunately the grouping and alternation facilities provided by the regex engine are very capable, but when all else fails we can just perform a second match using a separate regular expression – supported by the tool or native language of your choice.