> ## Documentation Index
> Fetch the complete documentation index at: https://docs.xray.cool/llms.txt
> Use this file to discover all available pages before exploring further.

# substr

> `substr`函数主要是用来对目标字符串进行截取

## 函数原型

`func substr(s1 string, start int, length int) string`

### 参数介绍

| 参数名称 | 参数介绍 |
| - | - |
| s1 | 需要被分割的字符串 |
| start | 开始分割的位置 |
| length | 分割长度 |

## 举例

| 待转换数据 | 转换语句 | 输出结果 |
| - | - | - |
| `abcdefg` | `substr("abcdefg", 1, 2)` | `bc` |
| `abcdefg` | `substr("abcdefg", 100, 2)` | `""` |
| `abcdefg` | `substr("abcdefg", 1, 6)` | `bcdefg` |
| `abcdefg` | `substr("abcdefg", 1, 8)` | `bcdefg` |
| `abcdefg` | `substr("abcdefg", -1, 100)` | `Error: "invalid substr index"` |
| `abcdefg` | `substr("abcdefg", 1, -100)` | `Error: "invalid substr index"` |
| `abcdefg` | `substr("abcdefg", 0, 0)` | `Error: "invalid substr index"` |


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