udev_example3.c

/* udev_example3.c
 *
 * Copyright (C) 2014-2021 Robert Milasan <robert@linux-source.org>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * This example monitors udev events for 'net' subsystem using libudev API.
 *
 */

#include <stdio.h>
#include <unistd.h>
#include <libudev.h>

int main()
{
	struct udev *udev;
	struct udev_device *dev;
   	struct udev_monitor *mon;
	int fd;

	/* create udev object */
	udev = udev_new();
	if (!udev) {
		fprintf(stderr, "Can't create udev\n");
		return 1;
	}

	mon = udev_monitor_new_from_netlink(udev, "udev");
	udev_monitor_filter_add_match_subsystem_devtype(mon, "net", NULL);
	udev_monitor_enable_receiving(mon);
	fd = udev_monitor_get_fd(mon);

	while (1) {
		fd_set fds;
		struct timeval tv;
		int ret;

		FD_ZERO(&fds);
		FD_SET(fd, &fds);
		tv.tv_sec = 0;
		tv.tv_usec = 0;

		ret = select(fd+1, &fds, NULL, NULL, &tv);
		if (ret > 0 && FD_ISSET(fd, &fds)) {
			dev = udev_monitor_receive_device(mon);
			if (dev) {
				printf("I: ACTION=%s\n", udev_device_get_action(dev));
				printf("I: DEVNAME=%s\n", udev_device_get_sysname(dev));
				printf("I: DEVPATH=%s\n", udev_device_get_devpath(dev));
				printf("I: MACADDR=%s\n", udev_device_get_sysattr_value(dev, "address"));
				printf("---\n");

				/* free dev */
				udev_device_unref(dev);
			}
		}
		/* 500 milliseconds */
		usleep(500*1000);
	}
	/* free udev */
	udev_unref(udev);

	return 0;
}