Host name resolution
| -- | ---------- | ------------------ | ---------------------------------- |
| * | HOSTS | host/addr,... | private host/address mapping |
| RESOLV | file,nis,dns,sys | the order of resolvers to be used | |
| RES_WAIT | sec:host | wait for resolver to be ready | |
| RES_CONF | URL | where resolv.conf is | |
| RES_NS | host[:port] | DNS server to be used | |
| RES_AF | 46 | 64 | 4 | 6 | Address families (IPv4/v6) to be retrieved | |
| RES_RR | HostList | enable Round Robin of IP-addresses | |
| RES_VRFY | "" | enable double check of reverse resolution | |
| RES_DEBUG | number | debugging level of name resolution |