# FCALL

```json metadata
{
  "schema_version": 2,
  "title": "FCALL",
  "description": "Invokes a function.",
  "categories": ["docs","develop","stack","oss","rs","rc","oss","kubernetes","clients"],
  "arguments": [{"display_text":"function","name":"function","type":"string"},{"display_text":"numkeys","name":"numkeys","type":"integer"},{"display_text":"key","key_spec_index":0,"multiple":true,"name":"key","optional":true,"type":"key"},{"display_text":"arg","multiple":true,"name":"arg","optional":true,"type":"string"}],
  "syntax_fmt": "FCALL function numkeys [key [key ...]] [arg [arg ...]]",
  "complexity": "Depends on the function that is executed.",
  "group": "scripting",
  "command_flags": ["noscript","stale","skip_monitor","no_mandatory_keys","movablekeys"],
  "acl_categories": ["@slow","@scripting"],
  "since": "7.0.0",
  "arity": -3,
  "key_specs": [{"RW":true,"access":true,"begin_search":{"spec":{"index":2},"type":"index"},"find_keys":{"spec":{"firstkey":1,"keynumidx":0,"keystep":1},"type":"keynum"},"notes":"We cannot tell how the keys will be used so we assume the worst, RW and UPDATE","update":true}],
  "tableOfContents": {"sections":[{"id":"required-arguments","title":"Required arguments"},{"id":"optional-arguments","title":"Optional arguments"},{"id":"examples","title":"Examples"},{"id":"redis-software-and-redis-cloud-compatibility","title":"Redis Software and Redis Cloud compatibility"},{"id":"return-information","title":"Return information"}]}

,
  "codeExamples": []
}
```

Invoke a function.

Functions are loaded to the server with the [`FUNCTION LOAD`](https://redis.io/docs/latest/commands/function-load) command.
The first argument is the name of a loaded function.

The second argument is the number of input key name arguments, followed by all the keys accessed by the function.
In Lua, these input keys names are available to the function as a table that is the callback's first argument.

**Important:**
To ensure the correct execution of functions, both in standalone and clustered deployments, all the key names that a function accesses must be explicitly provided as input key arguments.
The function should only access keys whose names are given as input arguments.
Functions should never access keys with programmatically-generated names or based on the contents of data structures stored in the database.

Any additional input arguments should not represent names of keys.
These are regular arguments and are passed in a Lua table as the callback's second argument.

For more information please refer to the [Redis Programmability](https://redis.io/docs/latest/develop/programmability) and [Introduction to Redis Functions](https://redis.io/docs/latest/develop/programmability/functions-intro) pages.

## Required arguments

<details open><summary><code>function</code></summary>

The name of the function to call.

</details>

<details open><summary><code>numkeys</code></summary>

The number of key names that follow. Arguments after the keys are passed as regular arguments.

</details>

## Optional arguments

<details open><summary><code>key [key ...]</code></summary>

The key names the function accesses, provided to it via the Lua  `KEYS` global variable. There must be exactly `numkeys` of them.

</details>

<details open><summary><code>arg [arg ...]</code></summary>

Additional arguments provided to the function via the Lua `ARGV` variable.

</details>

## Examples

The following example will create a library named `mylib` with a single function, `myfunc`, that returns the first argument it gets.

```
redis> FUNCTION LOAD "#!lua name=mylib \n redis.register_function('myfunc', function(keys, args) return args[1] end)"
"mylib"
redis> FCALL myfunc 0 hello
"hello"
```

## Redis Software and Redis Cloud compatibility

| Redis<br />Software | Redis<br />Cloud | <span style="min-width: 9em; display: table-cell">Notes</span> |
|:----------------------|:-----------------|:------|
| <span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> | <span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> |  |

## Return information

**RESP2:**

The return value depends on the function that was executed.

**RESP3:**

The return value depends on the function that was executed.