Forget about the intricacies of the DNS spec. This should have seemed like a bad life choice in any event. Turning user input into a command line when all you really wanted to do was write a 0 byte file:sprintf(acfcommand, "/bin/touch %s/control/notlshosts/'%s'", info->pw_dir, partner_fqdn);fp = popen(acfcommand, "r");