select函数应用场景1

将标准输入keyboard作为fd加入到fd_set中去。

#include    

#include    

#include    

#include

#include

#include

#include

#include

#include

#include    

#include

using namespace std;

int main ()

{

int keyboard;

int ret,i;

char c;

fd_set readfd;

struct timeval timeout;

keyboard = open("/dev/tty",O_RDONLY | O_NONBLOCK);

assert(keyboard>0);

printf("fd_set size = %d\n", sizeof(fd_set));

    FD_ZERO(&readfd);

while(1)

{

    timeout.tv_sec=2;

    timeout.tv_usec=0;

    FD_SET(keyboard,&readfd);

    ret=select(keyboard+1,&readfd,NULL,NULL,&timeout);

    //ret=select(keyboard+1,&readfd,NULL,NULL,NULL);

    printf("FD_ISEET before = %d, tv_sec =%d, tv_usec =%d", FD_ISSET(keyboard, &readfd), 

            timeout.tv_sec, timeout.tv_usec);

    if(FD_ISSET(keyboard,&readfd))

    {   

        read(keyboard,&c,1);

        if('\n'== c)

            continue;

        printf("hehethe input is %c\n",c);

        if ('q'==c)

        break;

    }   

}

}