This "-r" is an unnecessary GNU grep extension.
Unix philosophy is not to duplicate functionalities in multiple commands, but to have instead specialized commands that do well one thing and work easily together.
You can do something like this:
Code:
find . -type f -exec grep somepattern {} +
Of course, if you insist wanting a "grep -r" for Solaris, just install GNU grep on it, Unix philosophy is also about freedom of choice