How can I install getent on Snow Leopard?
dscacheutil is probably the best way to do this. It doesn't emulate the usual search process, it uses it, so you'll actually get the same results as a standard lookup (including caching, /etc/hosts, computer records in directory services, DNS, mDNS for .local names, etc).

$ dscacheutil -q host -a name www.apple.com
name: e3191.c.akamaiedge.net
alias: www.apple.com www.isg-apple.com.akadns.net www.apple.com.edgekey.net 
ip_address: 69.192.45.15

$ dscacheutil -q host -a name gordons-mbp.local
name: gordons-mbp.local
ipv6_address: fe80:5::e6ce:8fff:fe50:136

name: gordons-mbp.local
ip_address: 192.168.10.249

$ dscacheutil -q host -a ip_address 127.0.0.1
name: localhost
alias: 1.0.0.127.in-addr.arpa 
ip_address: 127.0.0.1

$ dscacheutil -q user -a name gordon
name: gordon
password: ********
uid: 501
gid: 20
dir: /Users/gordon
shell: /bin/bash
gecos: Gordon Davisson