# ARSET

> Set contiguous array values from an index.

Use `ARSET` to write one or more values into an array, starting at a given index.

The first value goes to `<index>`, the next to `<index> + 1`, and so on, so a batch of readings can be placed at a known offset in one call. Any slot in the range that was empty becomes occupied, and any slot that already held a value is overwritten. The reply counts only the slots that were newly occupied, which makes it a cheap way to tell how much of a write was new data rather than a correction.

Writing past the end of the array does not shift anything: an array is sparse, so the slots between the previous highest index and the new one simply stay empty. `ARSET` never moves the append cursor used by [`ARINSERT`](/redis/commands/array/arinsert), so mixing positional writes with appends is safe.

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

## Syntax

```redis
ARSET <key> <index> <value> [<value> ...]
```

## Arguments

| Argument | Required | Repeatable | Description |
| --- | --- | --- | --- |
| `<key>` | Yes | No | Array key targeted by the command. |
| `<index>` | Yes | No | Zero-based index of the first value. Must be between `0` and `18446744073709551614`. |
| `<value>` | Yes | Yes | Value to store. Repeat to fill consecutive indexes starting at `<index>`. |

## Important points

- The reply counts newly occupied slots only. Overwriting an existing value contributes `0`.
- An index outside the supported range, or a batch whose last index would exceed it, returns `ERR invalid array index`.

## 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 |
| RESP3 | Integer |

<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
ARSET my-array 0 hello world
```

</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.arset("my-array", 0, "hello", "world");
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.arSet("my-array", 0, ["hello", "world"]);
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.arset("my-array", 0, "hello", "world")
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.ARSet(context.Background(), "my-array", 0, "hello", "world").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.arset("my-array", 0, "hello", "world");
  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("ARSET");
    command.arg("my-array");
    command.arg("0");
    command.arg("hello");
    command.arg("world");
    let result: redis::Value = command.query(&mut connection)?;
    println!("{result:?}");
    Ok(())
}
```

</Accordion>

</AccordionGroup>