> For the complete documentation index, see [llms.txt](https://doc.open-tx.org/opentx-lua-reference-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.open-tx.org/opentx-lua-reference-guide/part_ii_-_opentx_lua_api_programming_guide/run_function_syntax.md).

# Run Function Syntax

The run function is the function that is periodically called for the lifetime of script execution. Syntax of the run function is different between [mix scripts](/opentx-lua-reference-guide/part_i_-_script_type_overview/mix.md) and [telemetry scripts](/opentx-lua-reference-guide/part_i_-_script_type_overview/telemetry.md).

## Run Function for Mix Scripts

```lua
local function <run_function_name>([first input, [second input], …])

   -- if mix has no return values
   return

   -- if mix has two return values
   return value1, value2

end
```

* **Input parameters:**

  zero or more input values, their names are arbitrary, their meaning and order is defined by the input table. (see [Input Table Syntax](/opentx-lua-reference-guide/part_ii_-_opentx_lua_api_programming_guide/input_table_syntax.md))
* **Return values:**
  * none - if output table is empty (i.e. script has no output)

    values\
    &#x20;\- or -
  * comma separated list of output values, their order and meaning is defined by the output table. (see [Output Table Syntax](/opentx-lua-reference-guide/part_ii_-_opentx_lua_api_programming_guide/output_table_syntax.md))

## Run Function for Telemetry Scripts

```lua
local function <run_function_name>(key-event)
  return 0 -- values other than zero will halt the script
end
```

* **Input parameters:**

  The *key-event* parameter indicates which transmitter button has been pressed (see [Key Events](/opentx-lua-reference-guide/part_iii_-_opentx_lua_api_reference/constants/key_events.md))
* **Return values:**

  A non-zero return value will halt the script