constantly polls until a file disappears

checkexist.c

#include <argp.h>
#include <stdio.h>
#include <stdlib.h>

#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

static char args_doc[] = "FILES to poll until missing";
static char doc[] = "poll for a file until it doesn't exist";
static error_t parse_opt(int key, char *arg, struct argp_state *state);
static struct argp_option options[] = {{0}};
static struct argp argp = {options, parse_opt, args_doc, doc, NULL, NULL, NULL};

#define ARRAYSIZE(x) ((sizeof(x)) / (sizeof(x[0])))

struct arguments {
	int nfiles;
	char *files[1000];
};

void clean_arguments(struct arguments *args) { free(args->files); }

int main(int argc, char **argv) {
	struct arguments __attribute__((__cleanup__(clean_arguments)))
	args = {};
	argp_parse(&argp, argc, argv, 0, 0, &args);

	for (;;) {
		int i;
		for (i = 0; i < args.nfiles; i++) {
			int fd = open(args.files[i], O_RDONLY);
			if (fd > 0) {
				close(fd);
				continue;
			}
			if (errno == ENOENT) {
				printf("file %s does not exist\n",
				       args.files[i]);
				exit(0);
			}
		}
	}
}

const char *argp_program_version = "checkexist 1.0";
const char *argp_program_bug_address = "<elazarl@gmail.com>";

/* Program documentation. */
static error_t parse_opt(int key, char *arg, struct argp_state *state) {
	/* Get the input argument from argp_parse, which we
	 *      know is a pointer to our arguments structure. */
	struct arguments *arguments = state->input;

	switch (key) {
		case ARGP_KEY_ARG:
			if (state->arg_num >=
			    ARRAYSIZE(
				arguments->files)) /* Too many arguments. */
				argp_usage(state);

			arguments->files[state->arg_num] = arg;
			break;

		case ARGP_KEY_END:
			if (state->arg_num < 1) /* Not enough arguments. */
				argp_usage(state);
			arguments->nfiles = state->arg_num;
			break;

		default:
			return ARGP_ERR_UNKNOWN;
	}
	return 0;
}