---
title: Side effects
description: A summary of side effects in the Flux functional data scripting language.
url: https://docs.influxdata.com/flux/v0/spec/side-effects/
estimated_tokens: 134
product: Flux
version: v0
---

# Side effects

Side effects can occur in one of two ways.

1. By reassigning built-in options
2. By calling a function that produces side effects

A function produces side effects when it is explicitly declared to have side effects or when it calls a function that itself produces side effects.

[Statements](/flux/v0/spec/statements/) [System built-ins](/flux/v0/spec/system-built-ins/)