Why doesn't grep -r also look in subdirectories when I search with a glob? [duplicate]

Grep with -r was not working for me.

I then made a test situation. The directory /home/den/backup now contains a file with the word washer in it. I also made a subdirectory within /home/den/backup. In that directory a file contains the word washer. The following should return two hits at /home/den/backup/great.txt and /home/den/backup/aaa/info.txt

If I issue

grep -r "washer" /home/den/backup/*.*

the result is one hit.

If I issue

grep -r "washer" /home/den/backup/aaa/*.*

the result is one hit.

Shouldn't the first one have also found the second one, which is in one if its sub-directories?

You can see what's happening here by setting the shell into debug mode using set -x

$ set -x
$ grep -r "washer" /home/steeldriver/backup/*.*
+ grep --color=auto -r washer /home/steeldriver/backup/great.txt
washer

i.e. the shell is expanding *.* and matching the single file great.txt - so grep searches that single file.

If you want to recursively search the whole directory, just give the directory as the argument:

$ grep -r "washer" /home/steeldriver/backup/
+ grep --color=auto -r washer /home/steeldriver/backup/
/home/steeldriver/backup/aaa/info.txt:washer
/home/steeldriver/backup/great.txt:washer

(You can turn debug mode off again using set +x)