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int tcgetattr(int fd, struct termios *termios_p);

1
int tcsetattr(int fd, int optional_actions, const struct termios *termios_p);

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int cfsetispeed(struct termios *termios_p, speed_t speed);
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int cfsetospeed(struct termios *termios_p, speed_t speed);
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int cfsetspeed(struct termios *termios_p, speed_t speed);

1
speed_t cfgetispeed(const struct termios *termios_p);
2
speed_t cfgetospeed(const struct termios *termios_p);

1
int tcflush(int fd, int queue_selector);

1
#include "fcntl.h"
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#include "termios.h"
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#include "unistd.h"
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#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
8

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#define RDBUF 512
10

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int set_opt(int fd, int speed, int databits, int stopbits, char parity,
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            struct termios *oldtio);
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int reset_opt(int fd, const struct termios *oldtio);
14

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int main(int argc, char *argv[]) {
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  if (argc != 2) {
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    fprintf(stderr, "Usage://\n");
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    exit(1);
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  }
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  const char *dev_path = argv[1];
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  int fd;
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  fd = open(dev_path, O_RDWR | O_NOCTTY);
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  if (fd < 0) {
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    perror("open()");
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    exit(1);
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  }
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  struct termios oldtio;
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  if (set_opt(fd, 115200, 8, 1, 'n', &oldtio) != 0) {
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    close(fd);
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    exit(1);
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  }
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  char readbuf[RDBUF];
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  char *linebuf = NULL;
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  size_t linesize = 0;
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  int get_n;
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  int w_n;
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  int r_n;
38

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  get_n = getline(&linebuf, &linesize, stdin);
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  tcflush(fd, TCIOFLUSH);
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  w_n = write(fd, linebuf, get_n);
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  if (w_n < 0) {
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    perror("write()");
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    exit(1);
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  }
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  if (tcdrain(fd) != 0) {
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    perror("tcdrain failed");
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  }
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  int total_r_n = 0;
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  while (1) {
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    r_n = read(fd, readbuf, RDBUF);
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    if (r_n > 0) {
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      readbuf[r_n] = '\0'; // 确保字符串结尾（可选）
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      write(STDOUT_FILENO, readbuf, r_n);
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    } else if (r_n == 0) {
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      printf("read timeout or no data\n");
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    } else {
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      perror("read failed");
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    }
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    total_r_n += r_n;
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    if (total_r_n >= get_n) {
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      break;
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    }
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  }
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  reset_opt(fd, &oldtio);
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  return 0;
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}
68

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// static struct termios oldtio;
70

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int set_opt(int fd, int speed, int databits, int stopbits, char parity,
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            struct termios *oldtio) {
73

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  struct termios newtio;
75

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  if (tcgetattr(fd, oldtio) < 0) {
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    perror("tcgetattr()");
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    exit(1);
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  }
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  memcpy(&newtio, &oldtio, sizeof(struct termios));
81

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  newtio.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG | IEXTEN);
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  newtio.c_iflag &= ~(IXON | IXOFF | IXANY | ICRNL | INLCR | IGNCR);
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  newtio.c_oflag &= ~OPOST;
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  newtio.c_cflag |= (CLOCAL | CREAD);
86

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  speed_t speed_;
88

89
  switch (speed) {
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  case 9600:
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    speed_ = B9600;
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    break;
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  case 19200:
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    speed_ = B19200;
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    break;
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  case 38400:
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    speed_ = B38400;
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    break;
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  case 57600:
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    speed_ = B57600;
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    break;
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  case 115200:
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    speed_ = B115200;
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    break;
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  default:
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    perror("ERROR");
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    exit(1);
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  }
109

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  cfsetispeed(&newtio, speed_);
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  cfsetospeed(&newtio, speed_);
112

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  newtio.c_cflag &= ~CSIZE;
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  newtio.c_cflag &= ~PARENB;
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  newtio.c_cflag &= ~CSTOPB;
116

117
  switch (databits) {
118
  case 7:
119
    newtio.c_cflag |= CS7;
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    break;
121
  case 8:
122
    newtio.c_cflag |= CS8;
123
    break;
124
  default:
125
    fprintf(stderr, "Unsupported data size\n");
126
    return -1; // 改进：返回错误码
127
  }
128

129
  switch (parity) {
130
  case 'o':
131
  case 'O':
132
    newtio.c_cflag |= PARENB;
133
    newtio.c_cflag |= PARODD;
134
    newtio.c_iflag |= (INPCK | ISTRIP);
135
    break;
136
  case 'e':
137
  case 'E':
138
    newtio.c_cflag |= PARENB;
139
    newtio.c_cflag &= ~PARODD;
140
    newtio.c_iflag |= (INPCK | ISTRIP);
141
    break;
142
  case 'n':
143
  case 'N':
144
    newtio.c_cflag &= ~PARENB;
145
    break;
146
  default:
147
    newtio.c_cflag &= ~PARENB;
148
    break;
149
  }
150

151
  if (stopbits == 2) {
152
    newtio.c_cflag |= CSTOPB;
153
  }
154

155
  newtio.c_cc[VTIME] = 1;
156
  newtio.c_cc[VMIN] = 0;
157

158
  tcflush(fd, TCIFLUSH);
159
  if (tcsetattr(fd, TCSANOW, &newtio) < 0) {
160
    perror("tcsetattr()");
161
    exit(1);
162
  }
163
  return 0;
164
}
165

166
int reset_opt(int fd, const struct termios *oldtio) {
167

168
  tcsetattr(fd, TCSANOW, oldtio);
169
  return 0;
170
}