grep on Windows 7 Invalid Argument

I am using grep from Gnuwin32 on Windows.

Doing:

grep -r INSERT *.sql

Yields:

grep: *.sql: Invalid argument

Any idea why?

Answer

According to the Grep manual:

-r with grep is recursive directory searching, so to use it you specify the starting directory, not a file mask.

e.g.:

grep -r INSERT . would look at all files for INSERT, starting at the current directory (.) and recursively working its way through the sub-folders.

To specify recursive folder checking and specify a file wildcard to limit searches, you can use the --include option:

grep -r --include "*.sql" INSERT .

Similar question/info over on StackOverflow: How do I grep recursively?