如何在Linux Shell中使用反引号？

Question

摘自《 Bash初学者指南》：

3.4.5. Command substitution

Command substitution allows the output of a command to replace the command itself. Command substitution
occurs when a command is enclosed like this:

$(command)

or like this using backticks:

\`command`

Bash performs the expansion by executing COMMAND and replacing the command substitution with the
standard output of the command, with any trailing newlines deleted. Embedded newlines are not deleted, but
they may be removed during word splitting.

    franky ~> echo `date`
    Thu Feb 6 10:06:20 CET 2003



When the old−style backquoted form of substitution is used, backslash retains its literal meaning except when
followed by "$", "`", or "\".

The first backticks not preceded by a backslash terminates the command substitution.

When using the "$(COMMAND)" form, all characters between the parentheses make up the
command; none are treated specially.

在这段中，有一个我听不懂的句子。

The first backticks not preceded by a backslash terminates the command substitution.

您能否提供示例以更详细地说明它？ 非常感谢你！

Answer 1

作者指的是第一个没有逃脱的背景。

虚拟示例：

echo `command \` arg`

首先，命令和arg之间的反引号用反斜杠转义，因此替换由最后一个反引号关闭。