Linux 套接字编程

select 可以感知文件表述符集合中的变化，如果办fd0（即标准输入）放入select的read fd set，发现只有按回车的时候select才会返回。查了下要把终端的缓冲大小设为1，这样就能实现击键后马上反应了。

#include <stdio.h>
#include <stdlib.h>

#include <unistd.h>
#include <errno.h>
#include <termio.h>

#include <sys/time.h>
#include <sys/types.h>

#define BUF_SIZE 256

void setup_terminal(struct termios* old_args);

void reset_terminal(struct termios* old_args);

int main() {
        struct termios old_args;

        setup_terminal(&old_args);

        fd_set rfds;
        int sres = 0;

        char buffer[BUF_SIZE];
        int nread = 0;

        for (;;) {
                /* reset read file descriptor set */
                FD_ZERO(&rfds);
                /* add standard input file descriptor to the set */
                FD_SET(0, &rfds);

                /* do blocking select */
                printf("
select begin
");
                sres = select(0 + 1, &rfds, NULL, NULL, NULL);
                printf("
select return
");

                if (sres < 0) {
                        perror("select error");
                        break;
                } else if (sres == 0) {
                        /* should not be here for blocked select without timeout*/
                        printf("select timeout
");
                } else {
                        if (FD_ISSET(0, &rfds)) {
                                nread = read(0, buffer, sizeof(buffer)-1);
                                if (nread <= 0) {
                                        perror("read error");
                                        break;
                                }
                                buffer[nread] = '';
                                printf("read string(%d): %s
", nread, buffer);
                        }
                }

        }
        reset_terminal(&old_args);
        return 0;
}

void setup_terminal(struct termios* old_args) {
        tcgetattr(0, old_args);

        struct termios new_args = *old_args;
        new_args.c_lflag &= ~ICANON;
        new_args.c_cc[VMIN] = 1;

        tcsetattr(0, TCSANOW, &new_args);
}

void reset_terminal(struct termios* old_args) {
        tcsetattr(0, TCSANOW, old_args);
}

记得很早之前也一致想实现这个功能，终于如愿，虽然和socket编程没什么太大关系。

参考：

http://tieba.baidu.com/p/685575698