Bash:C-d 的真正作用是什么？

Question

如果我在输入末尾按 C-d，输入似乎被刷新，但没有 EOF 发送到程序。但是，如果我再按一次 C-d，就会发送 EOF。

为什么我第一次按 C-d 时没有发送 EOF？这种行为记录在哪里？

为了试验自己玩 cat，这里有一个例子:

$ cat
abc<C-d>abc<C-d>
$

Answer 1

C-d 是 End-of-transmission (EOT) character :

In Unix the end-of-file character (by default EOT) causes the terminal driver to make available all characters in its input buffer immediately; normally the driver would collect characters until it sees an end-of-line character. If the input buffer is empty (because no characters have been typed since the last end-of-line or end-of-file), a program reading from the terminal reads a count of zero bytes. In Unix, such a condition is understood as having reached the end of the file.

在您的示例中，当您运行 cat 并键入几个字符后跟 C-d 时，此时键入的字符将发送到 cat 将它们打印到屏幕上。现在输入缓冲区为空，因此当您再次键入 C-d 时，cat 从缓冲区读取零字节并终止，因为已满足文件结束条件。