这将工作在Bash 4：
ls -l {,**/}*.ext
为了使双星号glob工作，需要设置globstar选项(默认：on)：
shopt -s globstar
从人bash：
globstar
If set,the pattern ** used in a filename expansion con‐
text will match a files and zero or more directories and
subdirectories. If the pattern is followed by a /,only
directories and subdirectories match.
