Regular Expression
| Category | Symbol | Name | Meaning | Example | Matches |
|---|---|---|---|---|---|
| 1. Wildcards & Character Classes | |||||
| Matching Characters | (text) | Literal | Matches exact text | cat |
"cat" |
. |
Dot | Matches any single character (except newline) | h.t |
"hat", "hot" | |
[ ] |
Brackets | List of allowed characters | b[ai]t |
"bat", "bit" | |
[^ ] |
Negation | Matches anything NOT in the list | [^a] |
Any char except 'a' | |
\d |
Digit | Any number 0-9 | \d\d |
"42", "99" | |
\w |
Word Char | Letter, number, or underscore | \w+ |
"User_1" | |
\s |
Space | Whitespace (space, tab, enter) | A\sB |
"A B" | |
| 2. Quantifiers (How Many?) | |||||
| Counting | * |
Star | 0 or more times | go*d |
"gd", "god" |
+ |
Plus | 1 or more times | go+d |
"god", "good" | |
? |
Question | 0 or 1 time (Optional) | colou?r |
"color", "colour" | |
{n} |
Exact Count | Matches exactly n times | \d{3} |
"123" | |
{n,} |
Min Count | Matches n or more times | \d{3,} |
"123", "12345" | |
{n,m} |
Range | Matches between n and m times | \d{2,4} |
"12", "1234" | |
.*? |
Lazy Match | Matches as little as possible | <.*?> |
Stops at first matching char | |
| 3. Anchors & Boundaries (Where?) | |||||
| Positioning | ^ |
Caret | Start of string/line | ^The |
Starts with "The" |
$ |
Dollar | End of string/line | end$ |
Ends with "end" | |
\b |
Word Boundary | The edge of a word (start or end) | \bcat\b |
"cat" (not "scat") | |
| 4. Groups & Logic | |||||
| Logic | Pipe | OR logic (Alternative) | dog | "cat" or "dog" | |
(...) |
Group | Groups characters or captures them | b)c | "ac" or "bc" | |
| 5. Special Characters | |||||
| Escaping | \ |
Backslash | Treats special characters as text | \. |
"." (actual dot) |