Yeah, timeout of 0, but no, not quite the same.
Basically, it's the same thing: we periodically check to see if any
data is available on the file descriptors that are important to us, and
process the data if its there.
The primary difference is if you have any number of file descriptors
larger than 1. If you set nonblocking and read, then you have a system
call overhead per file descriptor, regardless of whether there is data
available or not. If you use a polling select(), then you have one system
call overhead whether or not there's data (but just one: not one per
file descriptor) plus one system call for each file descriptor that actually
has data, but only when it has data. You get a big win using select()
if you have, say, 100 file descriptors that only have data once every
30 times you check.
But on the other hand, Ted's right that for most applications, you don't
want to poll in the first place: if your primary task is calculation,
kick a signal when data is available, and handle the file descriptor in
the signal handler, but if your primary task is the file descriptors, then
just go into a blocking select().