# 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
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
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
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
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
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
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
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
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>