dscacheutil

Directory Service (DNS) cache - Gather information, statistics, initiate queries, flush the cache.
dscacheutil replaces most of the functionality of thelookupd tool provided prior to OS X Leopard.

Syntax

      dscacheutil -q category [-a key value]

      dscacheutil -cachedump [-buckets] [-entries [category]]

      dscacheutil -configuration

      dscacheutil -flushcache

      dscacheutil -statistics

      dscacheutil -h

Options

     -h      List the options for calling dscacheutil

     -q category
             Initiate a query using standard calls.  These calls will either
             return results from the cache or go fetch live data and place
             them in the cache.  By default if no specific query is requested
             via -a then all results within that category will be returned.

     -a key value
             Optional flag to -q for a specific key with a value.

     -cachedump
             Dump an overview of the cache by default.  Additional flags will
             provide more detailed information.

     -buckets
             Use in conjunction with -cachedump to also print hash bucket
             usage of the current cache.

     -entries [category]
             Use in conjunction with -cachedump to dump detailed information
             about cache entries.  An optional category can be supplied to
             only see types of interest.

     -configuration
             Print current configuration information, such as the search pol-
             icy from Directory Service and cache parameters.

     -flushcache
             Flush the entire cache. This should only be used in extreme cases.
             Validation information is used within the cache along with other 
             techniques to ensure the OS has valid information
             available to it.

     -statistics
             Print statistics from the cache including an overview and
             detailed call statistics.  Some calls are not cached but are
             derived from other calls internally.  Cache hits and cache misses
             may not always be equal to external calls.  For example getad-
             drinfo is actually a combination of gethostbyname with other
             calls internally to the cache to maximize cache hit rate.

     Available categories and associated keys:

     group       name or gid

     host        name or ip_address (used for both IPv6 and IPv4)

     mount       name

     protocol    name or number

     rpc         name or number

     service     name or port

     user        name or uid

Examples

Edit the hosts file, then flush the DNS cache to have the changes take immediate effect:

$ sudo nano /private/etc/hosts
$ dscacheutil -flushcache

Lookup a user:

      $ dscacheutil -q user -a name jdoe
      name: jdoe
      password: ********
      uid: 501
      gid: 501
      dir: /Users/jdoe
      shell: /bin/csh
      gecos: John Doe

Lookup all users:

      $ dscacheutil -q user

Dump cache overview:

      $ dscacheutil -cachedump

Dump cache details with user entries:

      $ dscacheutil -cachedump -entries user

List the hosts that are currently in the DNS cache:

      $ dscacheutil -cachedump -entries Host |\
      grep "Key: h_" | \
      sed 's/^[ ]*Key: h_[a-z]*:\([^ ]*\)\( ipv[46]:1\)*/\1/g' | \
      sort -u

"Talent is hitting a target no-one else can hit, genius is hitting a target no-one else can see" - Schopenhauer

Related:

dscacheutil man page - Apple.com
DirectoryService(8)
dsmemberutil(1)
Windows equivalent: ipconfig / flushdns