# net_adm

###
Module

net_adm

###
Module Summary

Various Erlang net administration routines.

###
Description

This module contains various network utility functions.

###
Exports

####
dns_hostname(Host) -> {ok, Name} | {error, Host}

### Types

Host = atom() | string()
Name = string()

Returns the official name of Host, or {error, Host} if no such name is found. See also inet(3).

####
host_file() -> Hosts | {error, Reason}

### Types

Hosts = [Host :: atom()]
Reason =
file:posix() |
badarg | terminated | system_limit |
{Line :: integer(), Mod :: module(), Term :: term()}

Reads file .hosts.erlang, see section Files. Returns the hosts in this file as a list. Returns {error, Reason} if the file cannot be read or the Erlang terms on the file cannot be interpreted.

####
localhost() -> Name

### Types

Name = string()

Returns the name of the local host. If Erlang was started with command-line flag -name, Name is the fully qualified name.

####
names() -> {ok, [{Name, Port}]} | {error, Reason}

####
names(Host) -> {ok, [{Name, Port}]} | {error, Reason}

### Types

Host = atom() | string() | inet:ip_address()
Name = string()
Port = integer() >= 0
Reason = address | file:posix()

Similar to epmd -names, see erts:epmd(1). Host defaults to the local host. Returns the names and associated port numbers of the Erlang nodes that epmd registered at the specified host. Returns {error, address} if epmd is not operational.

Example:

    (arne@dunn)1> net_adm:names().
    {ok,[{"arne",40262}]}

####
ping(Node) -> pong | pang

### Types

Node = atom()

Sets up a connection to Node. Returns pong if it is successful, otherwise pang.

####
world() -> [node()]

####
world(Arg) -> [node()]

### Types

Arg = verbosity()
verbosity() = silent | verbose

Calls names(Host) for all hosts that are specified in the Erlang host file .hosts.erlang, collects the replies, and then evaluates ping(Node) on all those nodes. Returns the list of all nodes that are successfully pinged.

Arg defaults to silent. If Arg == verbose, the function writes information about which nodes it is pinging to stdout.

This function can be useful when a node is started, and the names of the other network nodes are not initially known.

Returns {error, Reason} if host_file() returns {error, Reason}.

####
world_list(Hosts) -> [node()]

####
world_list(Hosts, Arg) -> [node()]

### Types

Hosts = [atom()]
Arg = verbosity()
verbosity() = silent | verbose

Same as world/0,1, but the hosts are specified as argument instead of being read from .hosts.erlang.

###
Files

File .hosts.erlang consists of a number of host names written as Erlang terms. It is looked for in the current work directory, the user's home directory, and $OTP_ROOT (the root directory of Erlang/OTP), in that order.

The format of file .hosts.erlang must be one host name per line. The host names must be within quotes.

Example:

    'super.eua.ericsson.se'.
    'renat.eua.ericsson.se'.
    'grouse.eua.ericsson.se'.
    'gauffin1.eua.ericsson.se'.
    ^ (new line)