Check if there's incoming data in serial port linux (cbInQue for linux)

Question

I'm having a trouble with managing data coming into a linux serial port from an Arduino unit.

Basically, I have a working code to read and print out (or just store) but it is written for windows platform:

status is of type COMSTAT

int SerialPort::readSerialPort(char *buffer, unsigned int buf_size)
{
  DWORD bytesRead;
  unsigned int toRead = 0;
  Sleep(500);
  ClearCommError(this->handler, &this->errors, &this->status);

  if (this->status.cbInQue > 0) { //if there's something to read 
    if (this->status.cbInQue > buf_size) {//if there's something to read&bigger than buffer size
        toRead = buf_size; //read as much as buffer alows 
    }
    else toRead = this->status.cbInQue; //else just read as much as there is
}

if (ReadFile(this->handler, buffer, toRead, &bytesRead, NULL))
    return bytesRead; //return read data


return 0;//return 0 if nothing is there.
}

apart from Sleep() that is windows function, I was wondering if there is an equivalent linux function for status.cbInQue to understand if there is any data that is ready to be read in the port. Right now I just go ahead and read, without checking, and often I get nothing printed later in the program.

TLDR: is there cbInQue equivalent for linux?

Thanks

Answer 1

Yes, you will need your file descriptor and then use FIONREAD to see if anything is available.

Something like the following should work:

int available;
if( ioctl( fd, FIONREAD, &available ) < 0 ) {
    // Error handling here
}