linux - 脚本中 $(command) 和 `command` 之间的区别

Question

这个问题已经有答案了:

Command substitution: backticks or dollar sign / paren enclosed? [duplicate] (3 个回答)

已关闭 10 年前。

执行这样的命令有什么区别:

var=$(ls -alh /dir)

这样做:

var=`ls -alh /dir`

一种方法是否能够比另一种方法在更多的解释器中使用？

Answer 1

它们都是命令替换

第 3.5.4 节 http://www.gnu.org/software/bash/manual/bashref.html

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. The command substitution $(cat file) can be replaced by the equivalent but faster $(< file).

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

Command substitutions may be nested. To nest when using the backquoted form, escape the inner backquotes with backslashes.

If the substitution appears within double quotes, word splitting and filename expansion are not performed on the results.