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NAME

       slave - Functions to Starting and Controlling Slave Nodes

DESCRIPTION

       This  module provides functions for starting Erlang slave nodes. All slave nodes which are
       started by a master will terminate automatically  when  the  master  terminates.  All  TTY
       output  produced  at  the slave will be sent back to the master node. File I/O is done via
       the master.

       Slave nodes on other hosts than the current one are started with the program rsh. The user
       must be allowed to rsh to the remote hosts without being prompted for a password. This can
       be arranged in a number of ways (refer to the rsh documentation for details). A slave node
       started  on  the  same  host  as  the  master inherits certain environment values from the
       master, such as the current directory and the  environment  variables.  For  what  can  be
       assumed  about  the  environment  when  a  slave  is  started  on  another  host, read the
       documentation for the rsh program.

       An alternative to the rsh program can be specified on the command line to erl as  follows:
       -rsh Program.

       The  slave node should use the same file system at the master. At least, Erlang/OTP should
       be installed in the same place on both computers and the same version of Erlang should  be
       used.

       Currently, a node running on Windows NT can only start slave nodes on the host on which it
       is running.

       The master node must be alive.

EXPORTS

       start(Host) -> {ok, Node} | {error, Reason}

       start(Host, Name) -> {ok, Node} | {error, Reason}

       start(Host, Name, Args) -> {ok, Node} | {error, Reason}

              Types:

                 Host = Name = atom()
                 Args = string()
                 Node = node()
                 Reason = timeout | no_rsh | {already_running, Node}

              Starts a slave node on the host Host. Host names need not necessarily be  specified
              as  fully qualified names; short names can also be used. This is the same condition
              that applies to names of distributed Erlang nodes.

              The name of the started node will be Name@Host. If no name is  provided,  the  name
              will  be  the  same  as the node which executes the call (with the exception of the
              host name part of the node name).

              The slave node resets its user process so that all terminal I/O which  is  produced
              at the slave is automatically relayed to the master. Also, the file process will be
              relayed to the master.

              The Args argument is used to set erl command line arguments.  If  provided,  it  is
              passed to the new node and can be used for a variety of purposes. See erl(1)

              As  an  example, suppose that we want to start a slave node at host H with the node
              name Name@H, and we also want the slave node to have the following properties:

                * directory Dir should be added to the code path;

                * the Mnesia directory should be set to M;

                * the unix DISPLAY environment variable should be  set  to  the  display  of  the
                  master node.

              The following code is executed to achieve this:

              E = " -env DISPLAY " ++ net_adm:localhost() ++ ":0 ",
              Arg = "-mnesia_dir " ++ M ++ " -pa " ++ Dir ++ E,
              slave:start(H, Name, Arg).

              If  successful,  the function returns {ok, Node}, where Node is the name of the new
              node. Otherwise it returns {error, Reason}, where Reason can be one of:

                timeout:
                  The master node failed to get in contact with the slave node. This  can  happen
                  in a number of circumstances:

                  * Erlang/OTP is not installed on the remote host

                  * the file system on the other host has a different structure to the the master

                  * the Erlang nodes have different cookies.

                no_rsh:
                  There is no rsh program on the computer.

                {already_running, Node}:
                  A node with the name Name@Host already exists.

       start_link(Host) -> {ok, Node} | {error, Reason}

       start_link(Host, Name) -> {ok, Node} | {error, Reason}

       start_link(Host, Name, Args) -> {ok, Node} | {error, Reason}

              Types:

                 Host = Name = atom()
                 Args = string()
                 Node = node()
                 Reason = timeout | no_rsh | {already_running, Node}

              Starts  a  slave node in the same way as start/1,2,3, except that the slave node is
              linked to the currently executing process. If that process  terminates,  the  slave
              node also terminates.

              See start/1,2,3 for a description of arguments and return values.

       stop(Node) -> ok

              Types:

                 Node = node()

              Stops (kills) a node.

       pseudo([Master | ServerList]) -> ok

              Types:

                 Master = node()
                 ServerList = [atom()]

              Calls  pseudo(Master, ServerList). If we want to start a node from the command line
              and set up a number of pseudo servers, an Erlang runtime system can be  started  as
              follows:

              % erl -name abc -s slave pseudo klacke@super x --

       pseudo(Master, ServerList) -> ok

              Types:

                 Master = node()
                 ServerList = [atom()]

              Starts  a  number  of pseudo servers. A pseudo server is a server with a registered
              name which does absolutely nothing but pass on all message to the real server which
              executes  at  a  master node. A pseudo server is an intermediary which only has the
              same registered name as the real server.

              For example, if we have started a slave node N and want  to  execute  pxw  graphics
              code  on  this  node,  we can start the server pxw_server as a pseudo server at the
              slave node. The following code illustrates:

              rpc:call(N, slave, pseudo, [node(), [pxw_server]]).

       relay(Pid) -> no_return()

              Types:

                 Pid = pid()

              Runs a pseudo server. This function never returns any value and the  process  which
              executes  the  function will receive messages. All messages received will simply be
              passed on to Pid.