1slave(3) Erlang Module Definition slave(3)
2
6 slave - Functions for starting and controlling slave nodes.
7
10 This module provides functions for starting Erlang slave nodes. All
11 slave nodes that are started by a master terminate automatically when
12 the master terminates. All terminal output produced at the slave is
13 sent back to the master node. File I/O is done through the master.
14 Slave nodes on other hosts than the current one are started with the
16 ssh program. The user must be allowed to ssh to the remote hosts with‐
17 out being prompted for a password. This can be arranged in a number of
18 ways (for details, see the ssh documentation). A slave node started on
19 the same host as the master inherits certain environment values from
20 the master, such as the current directory and the environment vari‐
21 ables. For what can be assumed about the environment when a slave is
22 started on another host, see the documentation for the ssh program.
23 An alternative to the ssh program can be specified on the command line
25 to erl(1) as follows:
26 -rsh Program
28 Note that the command specified with the -rsh flag is treated as a file
30 name which may contain spaces. It is thus not possible to include any
31 command line options. The remote node will be launched as "$RSH" "$RE‐
32 MOTE_HOSTNAME" erl -detached -noinput ..., so the erl command must be
33 found in the path on the remote host.
34 The slave node is to use the same file system at the master. At least,
36 Erlang/OTP is to be installed in the same place on both computers and
37 the same version of Erlang is to be used.
38 A node running on Windows can only start slave nodes on the host on
40 which it is running.
41 The master node must be alive.
43
45 pseudo([Master | ServerList]) -> ok
46 Types:
48 Master = node()
50 ServerList = [atom()]
51 Calls pseudo(Master, ServerList). If you want to start a node
53 from the command line and set up a number of pseudo servers, an
54 Erlang runtime system can be started as follows:
55 % erl -name abc -s slave pseudo klacke@super x --
57 pseudo(Master, ServerList) -> ok
59 Types:
61 Master = node()
63 ServerList = [atom()]
64 Starts a number of pseudo servers. A pseudo server is a server
66 with a registered name that does nothing but pass on all message
67 to the real server that executes at a master node. A pseudo
68 server is an intermediary that only has the same registered name
69 as the real server.
70 For example, if you have started a slave node N and want to exe‐
72 cute pxw graphics code on this node, you can start server
73 pxw_server as a pseudo server at the slave node. This is illus‐
74 trated as follows:
75 rpc:call(N, slave, pseudo, [node(), [pxw_server]]).
77 relay(Pid) -> no_return()
79 Types:
81 Pid = pid()
83 Runs a pseudo server. This function never returns any value and
85 the process that executes the function receives messages. All
86 messages received are simply passed on to Pid.
87 start(Host) -> {ok, Node} | {error, Reason}
89 start(Host, Name) -> {ok, Node} | {error, Reason}
91 start(Host, Name, Args) -> {ok, Node} | {error, Reason}
93 Types:
95 Host = inet:hostname()
97 Name = atom() | string()
98 Args = string()
99 Node = node()
100 Reason = timeout | no_rsh | {already_running, Node}
101 Starts a slave node on host Host. Host names need not necessar‐
103 ily be specified as fully qualified names; short names can also
104 be used. This is the same condition that applies to names of
105 distributed Erlang nodes.
106 The name of the started node becomes Name@Host. If no name is
108 provided, the name becomes the same as the node that executes
109 the call (except the host name part of the node name).
110 The slave node resets its user process so that all terminal I/O
112 that is produced at the slave is automatically relayed to the
113 master. Also, the file process is relayed to the master.
114 Argument Args is used to set erl command-line arguments. If pro‐
116 vided, it is passed to the new node and can be used for a vari‐
117 ety of purposes; see erl(1).
118 As an example, suppose that you want to start a slave node at
120 host H with node name Name@H and want the slave node to have the
121 following properties:
122 * Directory Dir is to be added to the code path.
124 * The Mnesia directory is to be set to M.
126 * The Unix DISPLAY environment variable is to be set to the
128 display of the master node.
129 The following code is executed to achieve this:
131 E = " -env DISPLAY " ++ net_adm:localhost() ++ ":0 ",
133 Arg = "-mnesia_dir " ++ M ++ " -pa " ++ Dir ++ E,
134 slave:start(H, Name, Arg).
135 The function returns {ok, Node}, where Node is the name of the
137 new node, otherwise {error, Reason}, where Reason can be one of:
138 timeout:
140 The master node failed to get in contact with the slave
141 node. This can occur in a number of circumstances:
142 * Erlang/OTP is not installed on the remote host.
144 * The file system on the other host has a different struc‐
146 ture to the the master.
147 * The Erlang nodes have different cookies.
149 no_rsh:
151 No remote shell program was found on the computer. Note that
152 ssh is used by default, but this can be overridden with the
153 -rsh flag.
154 {already_running, Node}:
156 A node with name Name@Host already exists.
157 start_link(Host) -> {ok, Node} | {error, Reason}
159 start_link(Host, Name) -> {ok, Node} | {error, Reason}
161 start_link(Host, Name, Args) -> {ok, Node} | {error, Reason}
163 Types:
165 Host = inet:hostname()
167 Name = atom() | string()
168 Args = string()
169 Node = node()
170 Reason = timeout | no_rsh | {already_running, Node}
171 Starts a slave node in the same way as start/1,2,3, except that
173 the slave node is linked to the currently executing process. If
174 that process terminates, the slave node also terminates.
175 For a description of arguments and return values, see
177 start/1,2,3.
178 stop(Node) -> ok
180 Types:
182 Node = node()
184 Stops (kills) a node.
186Ericsson AB stdlib 3.16.1 slave(3)