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diff --git a/system/doc/system_principles/system_principles.xml b/system/doc/system_principles/system_principles.xml new file mode 100644 index 0000000000..27512a1660 --- /dev/null +++ b/system/doc/system_principles/system_principles.xml @@ -0,0 +1,236 @@ +<?xml version="1.0" encoding="latin1" ?> +<!DOCTYPE chapter SYSTEM "chapter.dtd"> + +<chapter> + <header> + <copyright> + <year>1996</year><year>2009</year> + <holder>Ericsson AB. All Rights Reserved.</holder> + </copyright> + <legalnotice> + The contents of this file are subject to the Erlang Public License, + Version 1.1, (the "License"); you may not use this file except in + compliance with the License. You should have received a copy of the + Erlang Public License along with this software. If not, it can be + retrieved online at http://www.erlang.org/. + + Software distributed under the License is distributed on an "AS IS" + basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See + the License for the specific language governing rights and limitations + under the License. + + </legalnotice> + + <title>System Principles</title> + <prepared></prepared> + <docno></docno> + <date></date> + <rev></rev> + <file>system_principles.xml</file> + </header> + + <section> + <title>Starting the System</title> + <p>An Erlang runtime system is started with the command <c>erl</c>:</p> + <pre> +% <input>erl</input> +Erlang (BEAM) emulator version 5.2.3.5 [hipe] [threads:0] + +Eshell V5.2.3.5 (abort with ^G) +1> </pre> + <p><c>erl</c> understands a number of command line arguments, see + <c>erl(1)</c>. A number of them are also described in this + chapter.</p> + <p>Application programs can access the values of the command line + arguments by calling one of the functions + <c>init:get_argument(Key)</c>, or <c>init:get_arguments()</c>. + See <c>init(3)</c>.</p> + </section> + + <section> + <title>Restarting and Stopping the System</title> + <p>The runtime system can be halted by calling <c>halt/0,1</c>. + See <c>erlang(3)</c>.</p> + <p>The module <c>init</c> contains function for restarting, + rebooting and stopping the runtime system. See <c>init(3)</c>.</p> + <pre> +init:restart() +init:reboot() +init:stop()</pre> + <p>Also, the runtime system will terminate if the Erlang shell is + terminated.</p> + </section> + + <section> + <marker id="BOOTSCRIPT"></marker> + <title>Boot Scripts</title> + <p>The runtime system is started using a <em>boot script</em>. + The boot script contains instructions on which code to load and + which processes and applications to start.</p> + <p>A boot script file has the extension <c>.script</c>. + The runtime system uses a binary version of the script. This + <em>binary boot script</em> file has the extension <c>.boot</c>.</p> + <p>Which boot script to use is specified by the command line flag + <c>-boot</c>. The extension <c>.boot</c> should be omitted. + Example, using the boot script <c>start_all.boot</c>:</p> + <pre> +% <input>erl -boot start_all</input></pre> + <p>If no boot script is specified, it defaults to + <c>ROOT/bin/start</c>, see Default Boot Scripts below.</p> + <p>The command line flag <c>-init_debug</c> makes the <c>init</c> + process write some debug information while interpreting the boot + script:</p> + <pre> +% <input>erl -init_debug</input> +{progress,preloaded} +{progress,kernel_load_completed} +{progress,modules_loaded} +{start,heart} +{start,error_logger} +...</pre> + <p>See <c>script(4)</c> for a detailed description of the syntax + and contents of the boot script.</p> + + <section> + <title>Default Boot Scripts</title> + <p>Erlang/OTP comes with two boot scripts:</p> + <taglist> + <tag><c>start_clean.boot</c></tag> + <item> + <p>Loads the code for and starts the applications Kernel and + STDLIB.</p> + </item> + <tag><c>start_sasl.boot</c></tag> + <item> + <p>Loads the code for and starts the applications Kernel, + STDLIB and SASL.</p> + </item> + </taglist> + <p>Which of <c>start_clean</c> and <c>start_sasl</c> to use as + default is decided by the user when installing Erlang/OTP using + <c>Install</c>. The user is asked "Do you want to use a minimal + system startup instead of the SASL startup". If the answer is + yes, then <c>start_clean</c> is used, otherwise + <c>start_sasl</c> is used. A copy of the selected boot script + is made, named <c>start.boot</c> and placed in + the <c>ROOT/bin</c> directory.</p> + </section> + + <section> + <title>User-Defined Boot Scripts</title> + <p>It is sometimes useful or necessary to create a user-defined + boot script. This is true especially when running Erlang in + embedded mode, see <seealso marker="#code_loading">Code Loading Strategy</seealso>.</p> + <p>It is possible to write a boot script manually. + The recommended way to create a boot script, however, is to + generate the boot script from a release resource file + <c>Name.rel</c>, using the function + <c>systools:make_script/1,2</c>. This requires that the source + code is structured as applications according to the OTP design + principles. (The program does not have to be started in terms of + OTP applications but can be plain Erlang).</p> + <p>Read more about <c>.rel</c> files in OTP Design Principles and + <c>rel(4)</c>.</p> + <p>The binary boot script file <c>Name.boot</c> is generated from + the boot script file <c>Name.script</c> using the function + <c>systools:script2boot(File)</c>.</p> + </section> + </section> + + <section> + <marker id="code_loading"></marker> + <title>Code Loading Strategy</title> + <p>The runtime system can be started in either <em>embedded</em> or + <em>interactive</em> mode. Which one is decided by the command + line flag <c>-mode</c>.</p> + <pre> +% <input>erl -mode embedded</input></pre> + <p>Default mode is <c>interactive</c>.</p> + <list type="bulleted"> + <item>In embedded mode, all code is loaded during system start-up + according to the boot script. (Code can also be loaded later + by explicitly ordering the code server to do so).</item> + <item>In interactive mode, code is dynamically loaded when first + referenced. When a call to a function in a module is made, and + the module is not loaded, the code server searches the code path + and loads the module into the system.</item> + </list> + <p>Initially, the code path consists of the current + working directory and all object code directories under + <c>ROOT/lib</c>, where <c>ROOT</c> is the installation directory + of Erlang/OTP. Directories can be named <c>Name[-Vsn]</c> and + the code server, by default, chooses the directory with + the highest version number among those which have the same + <c>Name</c>. The <c>-Vsn</c> suffix is optional. If an + <c>ebin</c> directory exists under the <c>Name[-Vsn]</c> + directory, it is this directory which is added to the code path.</p> + <p>The code path can be extended by using the command line flags + <c>-pa Directories</c> and <c>-pz Directories</c>. These will add + <c>Directories</c> to the head or end of the code path, + respectively. Example</p> + <pre> +% <input>erl -pa /home/arne/mycode</input></pre> + <p>The code server module <c>code</c> contains a number of + functions for modifying and checking the search path, see + <c>code(3)</c>.</p> + </section> + + <section> + <title>File Types</title> + <p>The following file types are defined in Erlang/OTP:</p> + <table> + <row> + <cell align="left" valign="middle"><em>File Type</em></cell> + <cell align="left" valign="middle"><em>File Name/Extension</em></cell> + <cell align="left" valign="middle"><em>Documented in</em></cell> + </row> + <row> + <cell align="left" valign="middle">module</cell> + <cell align="left" valign="middle"><c>.erl</c></cell> + <cell align="left" valign="middle">Erlang Reference Manual</cell> + </row> + <row> + <cell align="left" valign="middle">include file</cell> + <cell align="left" valign="middle"><c>.hrl</c></cell> + <cell align="left" valign="middle">Erlang Reference Manual</cell> + </row> + <row> + <cell align="left" valign="middle">release resource file</cell> + <cell align="left" valign="middle"><c>.rel</c></cell> + <cell align="left" valign="middle"><c>rel(4)</c></cell> + </row> + <row> + <cell align="left" valign="middle">application resource file</cell> + <cell align="left" valign="middle"><c>.app</c></cell> + <cell align="left" valign="middle"><c>app(4)</c></cell> + </row> + <row> + <cell align="left" valign="middle">boot script</cell> + <cell align="left" valign="middle"><c>.script</c></cell> + <cell align="left" valign="middle"><c>script(4)</c></cell> + </row> + <row> + <cell align="left" valign="middle">binary boot script</cell> + <cell align="left" valign="middle"><c>.boot</c></cell> + <cell align="left" valign="middle">-</cell> + </row> + <row> + <cell align="left" valign="middle">configuration file</cell> + <cell align="left" valign="middle"><c>.config</c></cell> + <cell align="left" valign="middle"><c>config(4)</c></cell> + </row> + <row> + <cell align="left" valign="middle">application upgrade file</cell> + <cell align="left" valign="middle"><c>.appup</c></cell> + <cell align="left" valign="middle"><c>appup(4)</c></cell> + </row> + <row> + <cell align="left" valign="middle">release upgrade file</cell> + <cell align="left" valign="middle"><c>relup</c></cell> + <cell align="left" valign="middle"><c>relup(4)</c></cell> + </row> + <tcaption>File Types</tcaption> + </table> + </section> +</chapter> + |