---
title: "system.serial.readUntil"
description: "Reads a byte at a time from a serial port until a delimiter character is encountered."
---

# system.serial.readUntil

> Reads a byte at a time from a serial port until a delimiter character is encountered.

This function is used in **Python Scripting**.

## Description
Reads a byte at a time from a serial port until a delimiter character is encountered. The read will block for up to timeout milliseconds before returning.

:::caution
If the delimiter is not found before the timeout period, then the buffer will dump, potentially resulting in data loss.
:::

## Client Permission Restrictions
This scripting function has no [Client Permission](../../../ignition-modules/vision/vision-project-properties/vision-project-properties.md#vision-permissions-properties) restrictions.

## Syntax
`system.serial.readUntil(port, delimiter, includeDelimiter, [timeout])`

### Parameters
Type | Parameter | Description 
------- | ------- | ------
String| `port` | The previously configured serial port to use.
Char| `delimiter` | The delimiter to read until.
Boolean| `includeDelimiter` | If true, the delimiter will be included in the return value.
Integer| `timeout` | Timeout in milliseconds. Default is 5000. [optional]

### Returns
**String** - Returns a String containing all 8-bit ASCII characters read until the delimiter was reached, and including the delimiter if the "includeDelimiter" parameter was true.
### Scope
Gateway, Vision Client, Perspective Session

## Code Example
```python title="Code Snippet"
# This example will read bytes from an open port called "COM1" until the delimiter character is reached.
port = "COM1"
delimiter = "$"
 
system.serial.readUntil(port,delimiter,True)
```