Introduction
This document collects useful regular expressions that are helpful for document processing.
Basics
Single-Character Match
| Regex | Rule | Can Match |
|---|
| A | A specified character | A |
| \u548c | A specified Unicode character | 和 |
| . | Any character | a, b, &, 0 |
| \d | Numbers 0~9 | 0~9 |
| \w | Lowercase and uppercase letters, numbers, and underscores | a~z, A~Z, 0~9, _ |
| \s | Space, Tab | Space, tab |
| \D | Non-number | a, A, &, _, …… |
| \W | Non \w | &, @, 中, …… |
| \S | Non \s | a, A, &, _, …… |
Multi-Character Match
| Regex | Rule | Can Match |
|---|
| A* | Any number of a character | Empty, A, AA, AAA, …… |
| A+ | At least 1 character | A, AA, AAA, …… |
| A? | 0 or 1 character | Empty, A |
| A{3} | 3 characters | AAA |
| A{2,3} | 2 to 3 characters | AA, AAA |
| A{2,} | At least n character | AA, AAA, AAAA, …… |
| A{0,3} | At most n character | Empty, A, AA, AAA |
Complex Match
| Regex | Rule | Can Match |
|---|
| ^ | Starts with | ^string |
| $ | Ends with | string$ |
| [ABC] | Any character in […] | A, B, C |
| [A-F0-9xy] | A character in the range | A, ……, F, 0, ……, 9, x, y |
[^a-f] | Any character not in the range | Non A ~ F |
| AB|CD|EF | AB or CD or EF | AB, CD, EF |
(?!_) | Cannot start with _ | |
(?!.*?_$) | Cannot end with _ | |
Use Cases
| Regex | Can Match |
|---|
[\u4e00-\u9fa5] | Chinese Character |
^[\u4e00-\u9fa5_a-zA-Z0-9]+$ | At least 1 Chinese/English/numbers/_ character |
[\u4e00-\u9fa5_a-zA-Z0-9]{4,10} | 4-10 Chinese/English/numbers/_ characters |
| Regex | Can Match |
|---|
\[[\s\S]*?\]\([\s\S]*?#[\s\S]*?\) | Links that end with #heading |
\[\w*.\w*\]\(#[\s\S]*?\) | Internal links within the same document |
| (https?|ftp|file)://[-A-Za-z0-9+&@#/%?=~_|!:,.;]+[-A-Za-z0-9+&@#/%=~_|] | URLs |
References