> ## Documentation Index
> Fetch the complete documentation index at: https://upstash-redis-1-18.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# ARNEXT

> Get the index the next append will use.

Use `ARNEXT` to read the index that the next [`ARINSERT`](/redis/commands/array/arinsert) would write to.

It reports the append cursor without moving it, so a producer can find out where its next write will land, or a reader can learn how far appends have progressed, without writing anything. The reply is `0` both when the key does not exist and when it exists but has never been appended to, since in both cases the next append goes to index `0`.

Because the cursor tracks appends rather than contents, `ARNEXT` is unaffected by [`ARSET`](/redis/commands/array/arset) writes and by deletions. [`ARSEEK`](/redis/commands/array/arseek) is the command that moves it.

See the [array command overview](/redis/commands/array/overview) for the data model these commands share.

## Syntax

```redis theme={null}
ARNEXT <key>
```

## Arguments

| Argument | Required | Repeatable | Description                        |
| -------- | -------- | ---------- | ---------------------------------- |
| `<key>`  | Yes      | No         | Array key targeted by the command. |

## Important points

* The reply is `0` for a key that does not exist and for one that has never been appended to.
* The reply is null when the cursor already sits on the highest supported index, so no further append is possible.

## Response

The reply reports the result of the operation. Error replies have the same shape in RESP2 and RESP3 and are surfaced as exceptions by the SDKs below.

| Protocol | Reply                                                                                       |
| -------- | ------------------------------------------------------------------------------------------- |
| RESP2    | Integer, or bulk string when the index exceeds the signed 64-bit range, or Null bulk string |
| RESP3    | Integer, or Big number when the index exceeds the signed 64-bit range, or Null              |

<Note>
  Client libraries often decode bulk strings, maps, sets, and numeric strings into language-native values. The table describes the Redis wire reply.
</Note>

## Examples

TCP examples use the TLS `REDIS_URL` from the Upstash console. REST examples use `UPSTASH_REDIS_REST_URL` and `UPSTASH_REDIS_REST_TOKEN`.

<AccordionGroup>
  <Accordion title="Redis CLI" icon="terminal">
    ```bash theme={null}
    ARNEXT my-array
    ```
  </Accordion>

  <Accordion title="@upstash/redis" icon="node-js" iconType="brands">
    <Note>
      This command is not supported yet in `@upstash/redis`.
    </Note>
  </Accordion>

  <Accordion title="upstash_redis" icon="python" iconType="brands">
    <Note>
      This command is not supported yet in `upstash_redis`.
    </Note>
  </Accordion>

  <Accordion title="ioredis" icon="node-js" iconType="brands">
    ```ts theme={null}
    import Redis from "ioredis";

    const redis = new Redis(process.env.REDIS_URL!);
    const result = await redis.arnext("my-array");
    console.log(result);
    ```
  </Accordion>

  <Accordion title="node-redis" icon="node-js" iconType="brands">
    ```ts theme={null}
    import { createClient } from "redis";

    const client = await createClient({ url: process.env.REDIS_URL })
      .on("error", console.error)
      .connect();
    const result = await client.arNext("my-array");
    console.log(result);
    ```
  </Accordion>

  <Accordion title="redis-py" icon="python" iconType="brands">
    ```python theme={null}
    import os
    import redis

    client = redis.from_url(os.environ["REDIS_URL"])
    result = client.arnext("my-array")
    print(result)
    ```
  </Accordion>

  <Accordion title="go-redis" icon="golang" iconType="brands">
    ```go theme={null}
    package main

    import (
        "context"
        "fmt"
        "os"

        "github.com/redis/go-redis/v9"
    )

    func main() {
        opts, err := redis.ParseURL(os.Getenv("REDIS_URL"))
        if err != nil {
            panic(err)
        }
        client := redis.NewClient(opts)
        result, err := client.ARNext(context.Background(), "my-array").Result()
        if err != nil {
            panic(err)
        }
        fmt.Println(result)
    }
    ```
  </Accordion>

  <Accordion title="jedis" icon="java" iconType="brands">
    ```java theme={null}
    import java.net.URI;

    import redis.clients.jedis.Jedis;

    try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) {
      Object result = jedis.arnext("my-array");
      System.out.println(result);
    }
    ```
  </Accordion>

  <Accordion title="redis-rs" icon="rust" iconType="brands">
    ```rust theme={null}
    fn main() -> redis::RedisResult<()> {
        let url = std::env::var("REDIS_URL").expect("REDIS_URL is not set");
        let client = redis::Client::open(url)?;
        let mut connection = client.get_connection()?;

        let mut command = redis::cmd("ARNEXT");
        command.arg("my-array");
        let result: redis::Value = command.query(&mut connection)?;
        println!("{result:?}");
        Ok(())
    }
    ```
  </Accordion>
</AccordionGroup>