nslookup is a network administration command-line tool available for many computer operating systems for querying the Domain Name System (DNS) to obtain domain name or IP address mapping or for any other specific DNS record. The Internet Systems Consortium has deprecated nslookup in favor of host and dig.
The name "nslookup" means "name server lookup". nslookup uses the operating system's local Domain Name System resolver library to perform its queries. Thus, it is configured automatically by the contents of the operating system file resolv.conf.
nslookup operates in interactive or non-interactive mode. When used interactively by invoking it without arguments or when the first argument is -(minus sign) and the second argument is host name or internet address of name server, the user issues parameter configurations or requests when presented with the nslookup prompt (
>).When no arguments are given, then the command queries to default server.The -(minus sign) invokes subcommands which are specified on command line and should precede nslookup commands. In non-interactive mode i.e.when first argument is name or internet address of the host being searched, parameters and the query are specified as command line arguments in the invocation of the program. The non interactive mode searches the information for specified host using default name server.
See also 
- dig (command), domain information groper
- whois, query tool for internet domains and IP addresses
- host (Unix), a simple utility for performing Domain Name System lookups
External links 
- Microsoft Windows
- Unix-like OSs