5.10 Regular Expressions
20210920
Regular expressions, or regex for short, are widely utilised through command line commands and in programs.
Visit https://regex101.com for an interactive tool to build and test regular expressions.
| Pattern | Explanation |
|---|---|
| . | anything, generally except newline (\n) |
| ^ | start of string or line |
| $ | end of string or line |
| + | 1 or more of previous pattern |
| * | 0 or more of previous pattern |
| ? | option previous pattern |
| {n} | exactly n previous pattern |
| {n,} | n or more previous pattern |
| {n,m} | n to m of previous pattern |
| \A | start of string |
| \b | word boundary |
| \B | not word boundary |
| \d | digit [0-9] |
| \D | not digit [^0-9] |
| \n | newline |
| \s | whitespace [\t\r\n\v\f] |
| \s | not whitespace [^\\t\\r\\n\\v\\f] |
| \t | tab |
| \w | word [A-Za-z0-9_] |
| \W | not word [^A-Za-z0-9_] |
| \Z | end of string |
| (…) | indexed group |
| (a | b) |
| (?:…) | group not indexed |
| [abc] | single char match a or b or c |
| [^abc] | single char not match a or b or c |
Your donation will support ongoing availability and give you access to the PDF version of this book. Desktop Survival Guides include Data Science, GNU/Linux, and MLHub. Books available on Amazon include Data Mining with Rattle and Essentials of Data Science. Popular open source software includes rattle, wajig, and mlhub. Hosted by Togaware, a pioneer of free and open source software since 1984. Copyright © 1995-2022 Graham.Williams@togaware.com Creative Commons Attribution-ShareAlike 4.0
