How to check if data come in from the socket without hanging there!!!

[KingdomHeart]

How do I check if there is data coming in from the socket without hang on to that socket.
Right now this is what I have

if(read(sockfd, recvline, MAXLINE)){
//processs.
//Code hang here until something come in from the socket. DONT WANT THIS
}


Here is what I want to happen but dont know how to do it


if(data coming in){
//process
}else{
//move on
}

[Cochrane]

With select(2). Basic case for just one socket (read the manpage for full information):

fd_set sockset;
FD_ZERO(&sockset);
FD_SET(your_socket_here, &sockset);
int result = select(your_socket_here + 1, sockset, NULL, NULL, NULL);
if (result < 0)
{
// You have an error
}
else if (result == 1)
{
// The socket has data. For good measure, it's not a bad idea to test further
if (FD_ISSET(your_socket_here, &sockset)
{
// Process
}
}
else
{
// Move on
}

That looks like a lot of code for such a basic task (and in fact, it is), but select can also tell you if one of many socket has something to say, as well as lots of other stuff.

[KittyMac]

You can also flag it as non-blocking by using fcntl


fcntl(fileDescriptor,
F_SETFL,
O_NONBLOCK);