> For the complete documentation index, see [llms.txt](https://lab-of-ontologies-language-proce.gitbook.io/ladsbook/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lab-of-ontologies-language-proce.gitbook.io/ladsbook/fu-lu/regular-expression.md).

# 正則表示法

一種確認文字模式的符號標記法。主要利用 **grep 來**完成。(主要用法見 `tldr grep`)

學習 regex 也可說是對「文字資料」學習一種新的解析能力。

```
$grep -i 愛 *.* | love.txt
```

### Meta-characters

#### 定錨 anchor: 開頭 (^) 結尾 ($)

#### 方括弧

```
$grep -h '[mk]ill' corpus*.txt
```

#### 否定

```
$grep -h '[^mk]ill' corpus*.txt
```

## 量詞 quantifiers

#### ? (0 或1) Match an Element Zero Times or One Time

```
```

#### \* (0 或 多) Match an Element Zero or More Times

```
```

#### ＋ (1 或 多) Match an Element One or More Times

```
```