Better yet, a subshell can contain another subshell, so expansions can be nested, too.

然而更有价值的是，子 Shell 可以包含另一个子 Shell，所以还可以进行嵌套扩展。

While it's common to run a subshell to pipe aggregated output to a single command, you can also use a subshell to expand a command in place, just like back ticks.

尽管通常运行子 Shell 将聚合的输出通过管道传递给单个命令，但您还可以使用子 Shell 对命令进行扩展，就像反勾号那样。

Here, the subshell command du -sh work | cut -f1 yields the total size of the work directory in a format compatible with pv.

在这里，子shell命令du-shwork |cut -f1以与pv兼容的格式生成工作目录的总大小。