Select not working Unix C

Question

fd_set read_fds;
struct timeval tv;
while(1){
    tv.tv_sec = 3;
    tv.tv_usec = 0;
    FD_ZERO(&read_fds);
    FD_SET(0,&read_fds);
    FD_SET(pipelogin,&read_fds);
    nfd = select(1,&read_fds,NULL,NULL,&tv);
    if(FD_ISSET(0,&read_fds)){
         printf("Comando"); }
         //comandos();
    if(FD_ISSET(pipelogin,&read_fds)){
         printf("Login"); }
         //VerificaLogin(pipelogin);
}

My function "comandos()" just read commands from user and do something and function VerificaLogin(pipelogin) just let the user login or not. I can only user "comando" once and VerificaLogin only works after the first "comando"...Can someone tell me what's wrong in here ? Sorry for bad english.

Answer 1

The select function is a status-reporting function. Unless the status changes, it will continue to report the same status.

Also, you should never use select with blocking sockets. That will only cause pain.