本文属于机器翻译版本。若本译文内容与英语原文存在差异，则一律以英文原文为准。

# \$1rtrim
<a name="rtrim"></a>

4.0 版的新增内容。

弹性集群不支持。

Amazon DocumentDB 中的`$rtrim`运算符用于从字符串中删除尾随字符。默认情况下，它会删除尾随的空格字符，但您也可以通过传递 chars 参数来指定一组要删除的字符。

**参数**
+ `input`: 要从中删除尾随空格字符的输入字符串。
+ `chars`:（可选）删除特定字符。

## 示例（MongoDB 外壳）
<a name="rtrim-examples"></a>

以下示例演示如何使用`$rtrim`运算符从字符串中删除尾随的指定字符 (” \$1”)。

**创建示例文档**

```
db.collection.insert([
  { "name": "John Doe*  ", "age": 30 },
  { "name": "Jane Smith  ", "age": 25 },
  { "name": "Bob Johnson", "age": 35 }
]);
```

**查询示例**

```
db.collection.aggregate([
  {
    $project: {
      _id: 0,
      name: { $rtrim: { input: "$name", chars: " *" } }, 
      age: 1
    }
  }
]);
```

**输出**

```
[
  { age: 30, name: 'John Doe' },
  { age: 25, name: 'Jane Smith' },
  { age: 35, name: 'Bob Johnson' }
]
```

## 代码示例
<a name="rtrim-code"></a>

要查看使用该`$rtrim`命令的代码示例，请选择要使用的语言的选项卡：

------
#### [ Node.js ]

```
const { MongoClient, Bson } = require('mongodb');

async function example() {
  const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');

  try {

    const db = client.db('test');
    const collection = db.collection('collection');  

    const pipeline = [
      {
        $project: {
          _id: 0,
          name: { $rtrim: { input: "$name", chars: " *" } },
          age: 1
        }
      }
    ];

    const results = await collection.aggregate(pipeline).toArray();
    console.dir(results, { depth: null });

  } catch (err) {
    console.error('Error occurred:', err);
  } finally {
    await client.close();
  }
}

example().catch(console.error);
```

------
#### [ Python ]

```
from pymongo import MongoClient

def example():
    client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')

    try:

        db = client.test
        collection = db.collection

        pipeline = [
            {
                "$project": {
                    "_id": 0,
                    "name": { "$rtrim": { "input": "$name", "chars": " *" } },
                    "age": 1
                }
            }
        ]

        results = collection.aggregate(pipeline)

        for doc in results:
            print(doc)

    except Exception as e:
        print(f"An error occurred: {e}")

    finally:
        client.close()

example()
```

------