svcok.c


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#include <stdlib.h>
#include <err.h>
#include <errno.h>
#include <sys/file.h>
#include <unistd.h>

char *dir = ".";

int
main(int argc, char **argv)
{
	int fd;

	if (argc > 1)
		dir = argv[1];

	if (chdir(dir) == -1)
		err(1, "chdir()");

	fd = open("supervise/lock", O_RDONLY);
	if (fd == -1) {
		if (errno == ENOENT)
			exit(100);
		else
			err(1, "open()");
	}

	if (flock(fd, LOCK_EX | LOCK_NB) == -1) {
		if (errno == EWOULDBLOCK)
			exit(0);
		else
			err(1, "flock()");
	} else 
		exit(100);

	return 0; /* Not reached */
}