Question

Is there any use in using the select() function ?

From my (small) experience I tend to believe that threads are enough.

So I wonder, is select() just a didactic tool for people who don’t yet know threads ?

Answer 1

Consider the following example. You have a moderately busy web server with something like 100K connections. You’re not using select or anything like it so you have one thread per connection, implying 100K threads which quickly becomes a problem.

Even if you tweak your system until it allows such a monstrosity, most of the threads will just wait on a socket. Wouldn’t it be better if there was a mechanism to notify you when a socket becomes interesting ?

Put another way, threading and select-like mechanisms are complementary. You just can’t use threads to replace the simple thing select does: monitoring file descriptors.