Question

I encounter one problem about the file system in the shell.
what’s difference between tmp/**/* and tmp/*?
I make the experiment in my system,
have this directory dir2

dir2
     -->dir1
         -->xx2
     -->ff.txt 

and I run ls dir2/*:

dir2/ff.txt

 dir2/dir1:
 xx2

then I run ls dir2/**/*:

dir2/dir1/xx2

So it means the ** is to ignore this directory(like ignore the dir1),
Can some one help me ?

Answer 1

I think there’s a formatting issue in the question test, but I’ll answer based on the question title and examples.

There shouldn’t be any difference between a single and double asterisk at any single level of the path. Either expression matches any name, except for hidden ones which start with a dot (this can be changed by shell options). So:

• tmp/**/* (equivalent to tmp/*/*) is expanded to all names which are nested two levels deep in tmp. The first asterisk expands only to directories and not files at the first level because it’s followed by a slash.
• tmp/* expands to anything nested one level deep inside tmp.

To this comes the fact that ls will list contents of directory if a directory is given on its command line. This can be overridden by adding -d option to ls.