我已经编写了一些代码，基本上使用正则表达式/dev/tty* 在 unix 系统上查找任何调制解调器，然后对于任何匹配项，查看是否可以打开端口，如果可以，则发送 AT 命令并检查响应消息是否包含字符“OK”。
该代码确实找到了调制解调器，但不幸的是它弄乱了终端显示。见下文。我注意到它还会打印 AT 命令 - 请参阅下面的输出。为什么我的终端显示改变了，我该如何解决？
运行程序后，如果您输入一个命令并输入，例如 ls，该命令不会显示，但当您按回车键时，您会看到输出。
代码如下:
#include <iostream>
#include <string>
#include <unordered_map>
#include <iomanip>
#include <memory>
#include <sstream>
#include <thread>
#include <iostream>
#include <filesystem>
#include <regex>
#include <unistd.h> // close
#include <fcntl.h> // open, O_RDWR, etc
#include <termios.h>
#include <string.h>
#include <sys/select.h> // timeouts for read
#include <sys/timeb.h> // measure time taken
int set_interface_attribs(int fd, int speed)
{
struct termios tty;
if (tcgetattr(fd, &tty) < 0) {
// Error from tcgetattr - can use strerror(errno)
return -1;
}
cfsetospeed(&tty, (speed_t)speed);
cfsetispeed(&tty, (speed_t)speed);
tty.c_cflag |= (CLOCAL | CREAD); /* ignore modem controls */
tty.c_cflag &= ~CSIZE;
tty.c_cflag |= CS8; /* 8-bit characters */
tty.c_cflag &= ~PARENB; /* no parity bit */
tty.c_cflag &= ~CSTOPB; /* only need 1 stop bit */
tty.c_cflag &= ~CRTSCTS; /* no hardware flowcontrol */
/* setup for non-canonical mode */
tty.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IXON);
tty.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
tty.c_oflag &= ~OPOST;
/* fetch bytes as they become available */
tty.c_cc[VMIN] = 1;
tty.c_cc[VTIME] = 1;
if (tcsetattr(fd, TCSANOW, &tty) != 0) {
// Error from tcsetattr- use strerror(errno)
return -1;
}
return 0;
}
long enumerate_ports(std::unordered_map <std::string, std::string>& ports) {
// ls /dev | grep ^tty.*
const std::regex my_filter( "^tty.*" );
std::string path = "/dev/";
for (const auto & entry : std::filesystem::directory_iterator(path)) {
std::smatch sm;
std::string tmp = entry.path().filename().string();
// if we have a regex match attempt to open port and send AT command
if (std::regex_match(tmp, sm, my_filter)) {
std::string portname = entry.path().string();
int fd = ::open(portname.c_str(), O_RDWR | O_NOCTTY);
if (fd < 0) {
// Error opening port
continue;
} else {
// port was opened successfully
// try to write AT command and do we get an OK response
// baudrate 9600, 8 bits, no parity, 1 stop bit
if(set_interface_attribs(fd, B9600) != 0) {
::close(fd);
continue;
}
int wlen = ::write(fd, "AT\r\n", 4);
if (wlen != 4) {
// Error from write
::close(fd);
continue;
}
// tcdrain() waits until all output written to the object referred
// to by fd has been transmitted.
tcdrain(fd);
fd_set set;
struct timeval timeout;
FD_ZERO(&set); /* clear the set */
FD_SET(fd, &set); /* add our file descriptor to the set */
timeout.tv_sec = 0;
timeout.tv_usec = 100000; // 100 milliseconds
// wait for data to be read or timeout
int rv = select(fd + 1, &set, NULL, NULL, &timeout);
if(rv > 0) { // no timeout or error
unsigned char buf[80];
const int bytes_read = ::read(fd, buf, sizeof(buf) - 1);
if (bytes_read > 0) {
buf[bytes_read] = 0;
unsigned char* p = buf;
// scan for "OK"
for (int i = 0; i < bytes_read; ++i) {
if (*p == 'O' && i < bytes_read - 1 && *(p+1) == 'K') {
// we have a positive response from device so add to ports
ports[portname] = "";
break;
}
p++;
}
}
}
::close(fd);
}
}
}
return ports.size();
}
int main() {
struct timeb start, end;
int diff;
ftime(&start);
// get list of ports available on system
std::unordered_map <std::string, std::string> ports;
long result = enumerate_ports(ports);
std::cout << "No. found modems: " << result << std::endl;
for (const auto& item : ports) {
std::cout << item.first << "->" << item.second << std::endl;
}
ftime(&end);
diff = (int) (1000.0 * (end.time - start.time)
+ (end.millitm - start.millitm));
printf("Operation took %u milliseconds\n", diff);
}
输出:
acomber@mail:~/Documents/projects/modem/serial/gdbplay$ ls
main.cpp main.o Makefile serial
acomber@mail:~/Documents/projects/modem/serial/gdbplay$ make serial
g++ -Wall -Werror -ggdb3 -std=c++17 -pedantic -c main.cpp
g++ -o serial -Wall -Werror -ggdb3 -std=c++17 -pedantic main.o -L/usr/lib -lstdc++fs
acomber@mail:~/Documents/projects/modem/serial/gdbplay$ sudo ./serial
[sudo] password for acomber:
AT
No. found modems: 1
/dev/ttyACM0->
Operation took 8643 milliseconds
acomber@mail:~/Documents/projects/modem/serial/gdbplay$
最佳答案
Why does this serial/modem code mess up my terminal display?
精确的答案要求您在执行代码之前发布终端的设置，即 stty -a。
The code does find a modem but unfortunately it messes up the terminal display.
最简单(即直接)的解决方法/解决方案是坚持保存然后恢复终端的 termios 设置的旧(但很少遵循)建议，如 this example .
您的代码中需要的简单更改类似于(请忽略 C 和 C++ 的混合；我只知道 C)以下补丁。
struct termios savetty;
int set_interface_attribs(int fd, int speed)
{
+ struct termios tty;
if (tcgetattr(fd, &tty) < 0) {
// Error from tcgetattr - can use strerror(errno)
return -1;
}
+ savetty = tty; /* preserve original settings for restoration */
cfsetospeed(&tty, (speed_t)speed);
cfsetispeed(&tty, (speed_t)speed);
然后在 enumerate_ports() 中，::close(fd); 的最后两个实例需要替换为将执行恢复的序列:
+ if (tcsetattr(fd, &savetty) < 0) {
+ // report cannot restore attributes
+ }
::close(fd);
After running the program, if you enter a command and enter, eg ls, the command is not shown ...
这显然是清除 ECHO 属性的结果。
“丢失”回车可能是由于清除了 OPOST。
其他被您的程序清除但可能预期由 shell 设置的显着属性是 ICANON、ICRNL 和 IEXTEN。
但是，与其尝试确定究竟需要撤消什么，正确且有保证的修复方法是简单地将 termios 设置恢复到其原始状态。
另一种(惰性)方法是在执行程序后使用 stty sane 命令。
关于c++ - 为什么这个串行/调制解调器代码会弄乱我的终端显示？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/56315825/