slave(3erl)
NAME
slave - Functions for starting and controlling slave nodes.
DESCRIPTION
This module provides functions for starting Erlang slave nodes. All slave nodes that are started by a master terminate automatically when the master terminates. All terminal output produced at the slave is sent back to the master node. File I/O is done through the master. Slave nodes on other hosts than the current one are started with the rsh program. 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 (for details, see the rsh documentation). 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, see the documentation for the rsh program. An alternative to the rsh program can be specified on the command line to erl(1) as follows: -rsh Program The slave node is to use the same file system at the master. At least, Erlang/OTP is to be installed in the same place on both computers and the same version of Erlang is to be used. A node running on Windows can only start slave nodes on the host on which it is running. The master node must be alive.
EXPORTS
pseudo([Master | ServerList]) -> ok
Types:
Master = node()
ServerList = [atom()]
Calls pseudo(Master, ServerList). If you 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 that does nothing but pass on all message
to the real server that executes at a master node. A pseudo
server is an intermediary that only has the same registered name
as the real server.
For example, if you have started a slave node N and want to
execute pxw graphics code on this node, you can start server
pxw_server as a pseudo server at the slave node. This is
illustrated as follows:
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 that executes the function receives messages. All
messages received are simply passed on to Pid.
start(Host) -> {ok, Node} | {error, Reason}
start(Host, Name) -> {ok, Node} | {error, Reason}
start(Host, Name, Args) -> {ok, Node} | {error, Reason}
Types:
Host = inet:hostname()
Name = atom() | string()
Args = string()
Node = node()
Reason = timeout | no_rsh | {already_running, Node}
Starts a slave node on 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 becomes Name@Host. If no name is
provided, the name becomes the same as the node that executes
the call (except the host name part of the node name).
The slave node resets its user process so that all terminal I/O
that is produced at the slave is automatically relayed to the
master. Also, the file process is relayed to the master.
Argument Args 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 you want to start a slave node at
host H with node name Name@H and want the slave node to have the
following properties:
* Directory Dir is to be added to the code path.
* The Mnesia directory is to be set to M.
* The Unix DISPLAY environment variable is to 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).
The function returns {ok, Node}, where Node is the name of the
new node, otherwise {error, Reason}, where Reason can be one of:
timeout:
The master node failed to get in contact with the slave
node. This can occur 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 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 = inet:hostname()
Name = atom() | string()
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.
For a description of arguments and return values, see
start/1,2,3.
stop(Node) -> ok
Types:
Node = node()
Stops (kills) a node.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
