FreeBSD/ismounted/ismounted.c

#include <stdlib.h>
#include <sys/stat.h>
#include <stdio.h>
#include <limits.h>
#include <unistd.h>
#include <getopt.h>
#include <locale.h>
#include <err.h>
#include <string.h>
#include <errno.h>
#include <getopt.h>
#include <signal.h>

static struct stat parent, current;

static int period;
static const char *path;

static void __attribute__((__noreturn__)) usage(void)
{
	fputs("\nUsage:\n", stderr);
	fputs("ismounted [-w timeout] folder\n", stderr);
	fputs("   -w: 1s periodic check until the process ran out of time.\n", stderr);

	exit(EXIT_SUCCESS);
}

static void sigHandler(int signo,
		siginfo_t *si __attribute__((unused)), void /* ucontext_t */ *uap __attribute__((unused)))
{
	switch (signo) {
		case SIGINFO:
			printf("Waiting for %s mount. %d seconds remaining.\n", path, period);
			break;
		case SIGALRM:
			/* Timer */
			--period;
			break;
		default:
			break;
	}
}

int main(int argc, char *argv[])
{
	int r;
	char *p_folder = NULL,  *a_folder = NULL;
	/* timer: optional */
	struct itimerspec its;
	timer_t timerid = 0;
	int ismounted = 0;
	/* signals */
	struct sigaction sa;
	/* handle options */
	int ch;
	struct option longopts[] = {
		{ "wait", required_argument, &period, 'w' },
		{ NULL,	0, NULL, 0 }
	};

	opterr = 0;
	while ((ch = getopt_long(argc, argv, "w:", longopts, NULL)) != -1) {
		switch (ch) {
			case 'w':
				period = atoi(optarg);
				break;
			case 0:
				/* long option */
				break;
		}
	}

	if (optind == (argc - 1))
		path = argv[optind];
	else
		usage();

	/* get real path name */
	a_folder = realpath(path, NULL);
	if (a_folder == NULL) 
		err(EXIT_FAILURE, "Path <%s> unreachable.", path);

	if (!strcmp("/", a_folder)) {
		printf("That's the root filesystem dude.");
		return EXIT_SUCCESS;
	}

	/* move to parent */
	strncat(a_folder, "/../", PATH_MAX - 1);
	p_folder = realpath(a_folder, NULL);

	r = stat(p_folder, &parent);
	if (r)
		err(EXIT_FAILURE, "Parent folder of <%s> is unreachable.", path);

	/* signal */
	sa.sa_handler = NULL;
	sa.sa_sigaction = &sigHandler;
	sa.sa_flags = SA_SIGINFO;
	sigemptyset(&sa.sa_mask);
	sigfillset(&sa.sa_mask);
	if (sigaction(SIGINFO, &sa, NULL))
		warn("SIGNFO not caught.");
	if (sigaction(SIGALRM, &sa, NULL))
		err(EXIT_FAILURE, "sigaction:ALARM");

	/* timer, if set */
	if ((period > 0) ) {
		its.it_interval.tv_sec = 1;
		its.it_interval.tv_nsec = 0;
		its.it_value.tv_sec = its.it_interval.tv_sec;
		its.it_value.tv_nsec = 0;
		if (timer_create(CLOCK_REALTIME, NULL, &timerid))
			err(EXIT_FAILURE,"timer_create failed.");
		if (timer_settime(timerid, 0, &its, NULL))
			err(EXIT_FAILURE, "timer_settime failed.");
	}

	/* proceed */
	printf("Waiting for folder %s to be mounted ...\n", path);
	while (1) {
		r = stat(path, &current);
		if (r)
			err(EXIT_FAILURE, "Current folder <%s> is unreachable.", path);

		ismounted = (current.st_dev != parent.st_dev);
		if (ismounted || (period == 0))
			break;

		pause();

	}

	printf("Folder path %s is %sa mount point.\n", path, (ismounted) ? "" : "*not* " );
	if (timerid)
		timer_delete(timerid);

	return EXIT_SUCCESS;
}