Question

when I use * in cp, I think it follows the same rule as regex.
so "cp temp/* test/" should copies everything over, however, when temp folder is empty it throws exception saying it cannot find file or directory, which indicte * cannot match “nothing”.

Then I create a file test.txt under temp and do:

cp temp/test.txt* test/

It works, which indicate * indeed match “nothing”.

I get confused about the behavior. Can anyone explain a little bit?

Thanks

Answer 1

What’s happening is the * expansion is done by your shell (bash probably). The pattern temp/testfile.txt* did match temp/testfile.txt (* matches zero or more characters), so bash passed that onto cp.

However, bash is set, by default, to pass the wildcard as-is on to the app if it doesn’t match anything (there’s an option called nullglob to turn this non-intuitive behavior off). So it passed temp/* literally to cp, which complained that it didn’t exist.