test.c

#include <stdio.h>
#include <stdlib.h>
#include <regex.h>
#include <unicode/uregex.h>

int main(int argc, char const *argv[])
{
	regex_t regex;
	if (regcomp(&regex, "\\w+", REG_ICASE | REG_EXTENDED)) {
		printf("Error compile\n");
		exit(255);
	}
	char *str = "1212131www31212";
	int matches = 0;
	int errorcode = regexec(&regex, str, matches, NULL, 0);
	if (errorcode) {
		printf("Error exec: %d\n", errorcode);
		exit(255);
	}
	printf("Matches found.\n");
	return 0;
}