question abt select() on FC 3

new user · 11-12-2005, 02:14 AM

Hi
I m having problem with the select call in my program.
IF i pass it FD_SETSIZE as first argument select (FD_SETSIZE, &readfs, NULL, NULL, NULL)it works fine but if i change it to something like
int fds= 4;
select (FD_SETSIZE, &readfs, NULL, NULL, NULL);
it never returns.
there is no error or anything.

btw i m using Linux FC 3
with gcc
gcc version 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)

any idea?

FLLinux · 11-12-2005, 12:25 PM

select (FD_SETSIZE, &readfs, NULL, NULL, NULL) with this argument set you are passing NULL as the last argument which is a timeout. And if you set this to NULL the select call will block just like a recv or accept call. If this is not what you want and you want select to return after a timeout then you will too create a timeval struct for the last argument with a timeout before each call to select (since select sets it to zero when it returns).

new user · 11-13-2005, 10:52 PM

my question was i about first argument FD_SETSIZE.
if i keep it to FD_SETSIZE my program would work OK
but if i change it to something like 2 or some userdefined value it never comes back frm select()
(in both cases the last argument is NULL)

FLLinux · 11-14-2005, 05:45 AM

So you are saying if you call select in the following way.
int fds= 4;
select (fds, &readfs, NULL, NULL, NULL);

It will never return. How many FDs have you put into readfs?