Increasing limit of FD_SETSIZE and select

Question

I want to increase FD_SETSIZE macro value for my system. Is there any way to increase FD_SETSIZE so select will not fail

Answer 1

It would be better (and easy) to replace with poll. Generally poll() is a simple drop-in replacement for select() and isn't limited by the 1024 of FD_SETSIZE...

fd_set fd_read;
int id = 42;
FD_ZERO(fd_read);
FD_SET(id, &fd_read);
struct timeval tv;
tv.tv_sec = 5;
tv.tv_usec = 0;
if (select(id + 1, &fd_read, NULL, NULL, &tv) != 1) {
   // Error.
}

becomes:

struct pollfd pfd_read;
int id = 42;
int timeout = 5000;
pfd_read.fd = id;
pfd_read.events = POLLIN;
if (poll(&pfd_read, 1, timeout) != 1) {
   // Error
}

You need to include poll.h for the pollfd structure.

If you need to write as well as read then set the events flag as POLLIN | POLLOUT.