backticks `` 和 $() 两个命令替换符的问题，急！！！

johnny_jiang

bash# echo `echo \\`                   #
bash# echo $(echo \\)                   # \

有哪位大虾能告诉我，为何两者输出的结果不同，为何用``时候，会没有任何输出，先谢了！

shannleon

When the old-style backquote form of substitution  is  used,  backslash
retains  its  literal  meaning except when followed by $, `, or \.  The
first backquote not preceded by a backslash terminates the command sub-
stitution.   When using the $(command) form, all characters between the
parentheses make up the command; none are treated specially.

从Bash手册上抄来的。以前还真没注意这个问题。

johnny_jiang

Post by shannleon
When the old-style backquote form of substitution  is  used,  backslash
retains  its  literal  meaning except when followed by $, `, or \.  The
first backquote not preceded by a backslash terminates the command sub-
stitution.   When using the $(command) form, all characters between the
parentheses make up the command; none are treated specially.

从Bash手册上抄来的。以前还真没注意这个问题。

多谢shannleon兄，

不过如你所说，The first backquote not preceded by a backslash terminates the command substitution.这句话让我有点模糊．而且我觉得这段话没说到重点．如果shannleon兄能够解释得更详细些，那感激不尽啊．

顶！

johnny_jiang

自己顶顶顶顶！