c - 为什么串口要设置 'no terminal should control the process'选项？

Question

fd = open("/dev/ttyUSB0",O_RDWR | O_NOCTTY);    
                               /* O_NOCTTY - No terminal will control the process   */

为什么要指定或不指定这个选项？它做什么和不做什么？

Answer 1

这在 GNU C library 的文档中得到了回答。 :

If the named file is a terminal device, don’t make it the controlling terminal for the process. See Job Control, for information about what it means to be the controlling terminal.

On GNU/Hurd systems and 4.4 BSD, opening a file never makes it the controlling terminal and O_NOCTTY is zero. However, GNU/Linux systems and some other systems use a nonzero value for O_NOCTTY and set the controlling terminal when you open a file that is a terminal device; so to be portable, use O_NOCTTY when it is important to avoid this.

也就是说，由于 USB 串行设备被视为终端，使用标志是您不希望它像终端并允许设备启动/停止恰好与给定用户连接的作业(例如，进程)。

进一步阅读:

• What is the purpose of the controlling terminal?