int
main(int argc, char *argv[])
{
	regex_t re;
	int e;
	char buf[1024], *ptr;
	regmatch_t rm[10];

	if (argc != 4) {
		fprintf(stderr, "Usage: %s <pattern> <substitute> <input>\n",
		    getprogname());
		return EXIT_FAILURE;
	}

	if ((e = regcomp(&re, argv[1], REG_EXTENDED)) != 0) {
		regerror(e, &re, buf, sizeof(buf));
		errx(EXIT_FAILURE, "regcomp(%s): %s\n", argv[1], buf);
	}
	switch (e = regexec(&re, argv[2], __arraycount(rm), rm, 0)) {
	case 0:
		if (aregsub(&ptr, argv[2], rm, argv[3]) < 0)
			err(EXIT_FAILURE, "substitution failed");
		printf("%s\n", ptr);
		free(ptr);
		break;
	case REG_NOMATCH:
		printf("no match: %s\n", argv[3]);
		break;
	default:
		regerror(e, &re, buf, sizeof(buf));
		errx(EXIT_FAILURE, "regexec(%s): %s\n", argv[3], buf);
	}
	return EXIT_SUCCESS;
}