Locking Linux Serial Port

Question

I have an issue that I\'m trying to solve regarding the serial port in Linux. I\'m able to open, read from, and close the port just fine. However, I want to ensure that I

Answer 1

In Linux, you can use the TIOCEXCL TTY ioctl to stop other open()s to the device from succeeding (they'll return -1 with errno==EBUSY, device or resource busy). This only works for terminals and serial devices, but it does not rely on advisory locking.

For example:

#include 
#include 
#include 
#include 
#include 
#include 
#include 

int open_device(const char *const device)
{
    int descriptor, result;

    if (!device || !*device) {
        errno = EINVAL;
        return -1;
    }

    do {
        descriptor = open(device, O_RDWR | O_NOCTTY);
    } while (descriptor == -1 && errno == EINTR);
    if (descriptor == -1)
        return -1;

    if (ioctl(descriptor, TIOCEXCL)) {
        const int saved_errno = errno;
        do {
            result = close(descriptor);
        } while (result == -1 && errno == EINTR);
        errno = saved_errno;
        return -1;
    }

    return descriptor;
}

Hope this helps.