> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/man/man4/pty.4.md).

# pty.4

`pty` — 旧式兼容伪终端驱动程序

## 名称

`pty`

## 概要

`device pty`

## 描述

`pty` 驱动程序为传统的 BSD 命名方案提供支持，该方案在 [pts(4)](/man/man4/pts.4.md) 取代它之前用于访问伪终端。这种传统命名在 Linux 中仍在使用。当打开设备 **`/dev/ptyXX`** 时，[pts(4)](/man/man4/pts.4.md) 驱动程序会创建新终端。同时会为此终端创建一个名为 **`/dev/ttyXX`** 的设备节点。

`pty` 驱动程序还提供了一个克隆式的 System V **`/dev/ptmx`** 设备。

新代码不应尝试使用此接口分配伪终端。提供它仅为兼容较旧的 C 库（在调用 posix\_openpt(2) 时会尝试打开此类设备）以及运行 Linux 二进制文件。

## 文件

BSD 风格的兼容伪终端驱动程序使用以下设备名：

**`/dev/pty[l-sL-S][0-9a-v]`** 伪终端主设备。

**`/dev/tty[l-sL-S][0-9a-v]`** 伪终端从设备。

**`/dev/ptmx`** 控制设备，打开时返回一个新的主伪终端的文件描述符。

## 诊断

无。

## 参见

posix\_openpt(2), [pts(4)](/man/man4/pts.4.md), [tty(4)](/man/man4/tty.4.md)

## 历史

伪终端驱动程序出现于 4.2BSD。

## 缺陷

与之前的实现不同，PTY 不再使用时即销毁主从设备节点。对不存在的主设备调用 stat(2) 已经会创建新的主设备节点。主设备只能通过打开并关闭来销毁。

`pty` 驱动程序无法卸载，因为它无法确定自己是否正在使用中。


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