read data into R with some constraints

I have a big data file (over 30,000 records) looks
like this:

100, 20, 46, 70
103,  0, 22, 45
117, -1, 34, 65
120, 15,  0, 25
113,  0,  -1, 32
142, -1, -1, 55
.....

I want to read only those records having positive
values in all of the  four
columns. That is, I don't want to read record # 3, 5,
and 6 into R.

Perhaps someone knows how to do this with R, but, if
I had to do it right now, I would pre-process with grep
before reading into R:

grep -v "-" myddata > myshorterdata

The "grep" tool is available on Unix and Linux.  If you have
Windows, it would be useful to get the "unix tools for windows",
which, unfornuately, I have just been unable to find after 10
minutes of searching www.gnu.org.