c - 无法获取串口配置的属性

Question

Helo，我一直在尝试使用 tcgetattr 检索串行端口的配置，并且我能够在第一次获得正确的值。当我更改相应参数的值时，我得到的返回值是以前返回的重复。如果有人知道请帮忙。当串行端口连接处于活动状态并正常工作时，我尝试了这个。

#include<termios.h>
#include<stdio.h>
#include<unistd.h>
#include<fcntl.h>
#include<string.h>

char *baudQuery(speed_t speed){
    static char   SPEED[20];
    switch (speed){
        case B4800:
            strcpy(SPEED, "B4800");
            return SPEED;
            break;
        case B9600:
            strcpy(SPEED, "B9600");
            return SPEED;
            break;
        case B19200:
            strcpy(SPEED, "B19200");
            return SPEED;
            break;
        case B38400:
            strcpy(SPEED, "B38400");
            return SPEED;
            break;
        case B57600:
            strcpy(SPEED, "B57600");
            return SPEED;
            break;
        case B115200:
            strcpy(SPEED, "B115200");
            return SPEED;
            break;
        default :
            strcpy(SPEED, "ERROR");
            return SPEED;
    }
}

main() {
    int fd;
    struct termios term;
    speed_t speed;
    term.c_cflag = B38400 | ~CSIZE | CS5  | PARENB | (~PARODD);
    term.c_lflag = ~(ICANON | ECHO | ECHOE);

    if((fd = open("/dev/ttyS1",O_RDWR)) <0)
        printf("Failed to open file\n");

    tcsetattr(fd,TCSANOW,&term);
    if (tcgetattr(fd, &term) != 0)
    perror("tcgetatt() error");
    else {
    speed = cfgetospeed(&term);
        printf("cfgetispeed() says the speed of stdin is %s\n",
    baudQuery(speed));
    tcgetattr(fd, &term);
    switch(term.c_cflag & CSIZE){
        case CS5:
        puts("Data Bits = 5");
        break;
        case CS6:
        puts("Data Bits = 6");
        break;
        case CS7:
        puts("Data Bits = 7");
        break;
        case CS8:
        puts("Data Bits = 8");
        break;
    }
    tcgetattr(fd, &term);

    if(term.c_cflag & (~PARENB))
    puts("No parity is used");
    if (term.c_cflag & (PARENB & (~PARODD)) )
    puts("Even parity is used");
    if (term.c_cflag & (PARODD & PARENB))
    puts("Odd parity is used");

    //Get the mode (Only part working correct!)
    if(term.c_lflag & ICANON)
        puts("Mode is canonical");
    else
        puts("Mode is non canonical");
    }
    close(fd);
}