bash - EOFD 是什么意思?

Question

在浏览 SO 时，我有时会看到 EOFD，例如:

ftp -vn <$hostname> <<EOFD

是的，我试过谷歌但没有成功，以防万一你想知道。

Answer 1

在 the question you reference 的上下文中, EOFD没有什么特别的意思，它只是 bash 的开始 here document .

来自Advanced Bash-Scripting Guide :

A here document is a special-purpose code block. It uses a form of I/O redirection to feed a command list to an interactive program or a command, such as ftp, cat, or the ex text editor.

COMMAND <<InputComesFromHERE
...
...
...
InputComesFromHERE

A limit string delineates (frames) the command list. The special symbol << precedes the limit string. This has the effect of redirecting the output of a command block into the stdin of the program or command. It is similar to interactive-program < command-file, where command-file contains

command #1
command #2
...

The here document equivalent looks like this:

interactive-program <<LimitString
command #1
command #2
...
LimitString

Choose a limit string sufficiently unusual that it will not occur anywhere in the command list and confuse matters.

所以在那个问题中，作者正在向 ftp 发送命令就像交互式地使用它一样。