#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>

int filename_ok(const char *);

int main(int argc, char *argv[])
{
	DIR *d;
	struct dirent *de;
	char fn[PATH_MAX];

	if (argc != 2) {
		fprintf(stderr, "usage: %s <path>\n", argv[0]);
		fprintf(stderr, "deletes all files that don't start with 3 digits in <path>\n");
		
		return 1;
	}
	
	if ((d = opendir(argv[1])) == NULL) {
		perror("opendir");
		return 1;
	}
	
	while ((de = readdir(d)) != NULL) {
		if (!filename_ok(de->d_name)) {
			sprintf(fn, "%s%s%s", argv[1], argv[1][strlen(argv[1]) - 1] == '/' ? "" : "/", de->d_name);
			
			if (unlink(fn) < 0) {
				if (errno == EISDIR)
					continue;
				perror("unlink");
			}
		}
	}
	
	closedir(d);
	
	return 0;
}

int filename_ok(const char *file)
{
	if (file == NULL) {
		fprintf(stderr, "I hate myself and want to die.\n");
		return 1;
	}
	
	if (!strcmp(file, "..") || !strcmp(file, "."))
		return 1;
	
	if (strlen(file) < 3)
		return 0;

	if (!isdigit(file[0]) || !isdigit(file[1]) || !isdigit(file[2]))
		return 0;
	
	return 1;
}