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diff --git a/erts/doc/src/init.xml b/erts/doc/src/init.xml new file mode 100644 index 0000000000..33364c709a --- /dev/null +++ b/erts/doc/src/init.xml @@ -0,0 +1,384 @@ +<?xml version="1.0" encoding="latin1" ?> +<!DOCTYPE erlref SYSTEM "erlref.dtd"> + +<erlref> + <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>init</title> + <prepared></prepared> + <docno></docno> + <date></date> + <rev></rev> + <file>init.xml</file> + </header> + <module>init</module> + <modulesummary>Coordination of System Startup</modulesummary> + <description> + <p>The <c>init</c> module is pre-loaded and contains the code for + the <c>init</c> system process which coordinates the start-up of + the system. The first function evaluated at start-up is + <c>boot(BootArgs)</c>, where <c>BootArgs</c> is a list of command + line arguments supplied to the Erlang runtime system from + the local operating system. See + <seealso marker="erts:erl">erl(1)</seealso>.</p> + <p><c>init</c> reads the boot script which contains instructions on + how to initiate the system. See + <seealso marker="sasl:script">script(4)</seealso> for more + information about boot scripts.</p> + <p><c>init</c> also contains functions to restart, reboot, and stop + the system.</p> + </description> + <funcs> + <func> + <name>boot(BootArgs) -> void()</name> + <fsummary>Start the Erlang runtime system</fsummary> + <type> + <v>BootArgs = [binary()]</v> + </type> + <desc> + <p>Starts the Erlang runtime system. This function is called + when the emulator is started and coordinates system start-up.</p> + <p><c>BootArgs</c> are all command line arguments except + the emulator flags, that is, flags and plain arguments. See + <seealso marker="erts:erl">erl(1)</seealso>.</p> + <p><c>init</c> itself interprets some of the flags, see + <seealso marker="#flags">Command Line Flags</seealso> below. + The remaining flags ("user flags") and plain arguments are + passed to the <c>init</c> loop and can be retrieved by calling + <c>get_arguments/0</c> and <c>get_plain_arguments/0</c>, + respectively.</p> + </desc> + </func> + <func> + <name>get_args() -> [Arg]</name> + <fsummary>Get all non-flag command line arguments</fsummary> + <type> + <v>Arg = atom()</v> + </type> + <desc> + <p>Returns any plain command line arguments as a list of atoms + (possibly empty). It is recommended that + <c>get_plain_arguments/1</c> is used instead, because of + the limited length of atoms.</p> + </desc> + </func> + <func> + <name>get_argument(Flag) -> {ok, Arg} | error</name> + <fsummary>Get the values associated with a command line user flag</fsummary> + <type> + <v>Flag = atom()</v> + <v>Arg = [Values]</v> + <v> Values = [string()]</v> + </type> + <desc> + <p>Returns all values associated with the command line user flag + <c>Flag</c>. If <c>Flag</c> is provided several times, each + <c>Values</c> is returned in preserved order.</p> + <pre> +% <input>erl -a b c -a d</input> +... +1> <input>init:get_argument(a).</input> +{ok,[["b","c"],["d"]]}</pre> + <p>There are also a number of flags, which are defined + automatically and can be retrieved using this function:</p> + <taglist> + <tag><c>root</c></tag> + <item> + <p>The installation directory of Erlang/OTP, <c>$ROOT</c>.</p> + <pre> +2> <input>init:get_argument(root).</input> +{ok,[["/usr/local/otp/releases/otp_beam_solaris8_r10b_patched"]]}</pre> + </item> + <tag><c>progname</c></tag> + <item> + <p>The name of the program which started Erlang.</p> + <pre> +3> <input>init:get_argument(progname).</input> +{ok,[["erl"]]}</pre> + </item> + <tag><c>home</c></tag> + <item> + <p>The home directory.</p> + <pre> +4> <input>init:get_argument(home).</input> +{ok,[["/home/harry"]]}</pre> + </item> + </taglist> + <p>Returns <c>error</c> if there is no value associated with + <c>Flag</c>.</p> + </desc> + </func> + <func> + <name>get_arguments() -> Flags</name> + <fsummary>Get all command line user flags</fsummary> + <type> + <v>Flags = [{Flag, Values}]</v> + <v> Flag = atom()</v> + <v> Values = [string()]</v> + </type> + <desc> + <p>Returns all command line flags, as well as the system + defined flags, see <c>get_argument/1</c>.</p> + </desc> + </func> + <func> + <name>get_plain_arguments() -> [Arg]</name> + <fsummary>Get all non-flag command line arguments</fsummary> + <type> + <v>Arg = string()</v> + </type> + <desc> + <p>Returns any plain command line arguments as a list of strings + (possibly empty).</p> + </desc> + </func> + <func> + <name>get_status() -> {InternalStatus, ProvidedStatus}</name> + <fsummary>Get system status information</fsummary> + <type> + <v>InternalStatus = starting | started | stopping</v> + <v>ProvidedStatus = term()</v> + </type> + <desc> + <p>The current status of the <c>init</c> process can be + inspected. During system startup (initialization), + <c>InternalStatus</c> is <c>starting</c>, and + <c>ProvidedStatus</c> indicates how far the boot script has + been interpreted. Each <c>{progress, Info}</c> term + interpreted in the boot script affects <c>ProvidedStatus</c>, + that is, <c>ProvidedStatus</c> gets the value of <c>Info</c>.</p> + </desc> + </func> + <func> + <name>reboot() -> void()</name> + <fsummary>Take down and restart an Erlang node smoothly</fsummary> + <desc> + <p>All applications are taken down smoothly, all code is + unloaded, and all ports are closed before the system + terminates. If the <c>-heart</c> command line flag was given, + the <c>heart</c> program will try to reboot the system. Refer + to <c>heart(3)</c> for more information.</p> + <p>To limit the shutdown time, the time <c>init</c> is allowed + to spend taking down applications, the <c>-shutdown_time</c> + command line flag should be used.</p> + </desc> + </func> + <func> + <name>restart() -> void()</name> + <fsummary>Restart the running Erlang node</fsummary> + <desc> + <p>The system is restarted <em>inside</em> the running Erlang + node, which means that the emulator is not restarted. All + applications are taken down smoothly, all code is unloaded, + and all ports are closed before the system is booted again in + the same way as initially started. The same <c>BootArgs</c> + are used again.</p> + <p>To limit the shutdown time, the time <c>init</c> is allowed + to spend taking down applications, the <c>-shutdown_time</c> + command line flag should be used.</p> + </desc> + </func> + <func> + <name>script_id() -> Id</name> + <fsummary>Get the identity of the used boot script</fsummary> + <type> + <v>Id = term()</v> + </type> + <desc> + <p>Get the identity of the boot script used to boot the system. + <c>Id</c> can be any Erlang term. In the delivered boot + scripts, <c>Id</c> is <c>{Name, Vsn}</c>. <c>Name</c> and + <c>Vsn</c> are strings.</p> + </desc> + </func> + <func> + <name>stop() -> void()</name> + <fsummary>Take down an Erlang node smoothly</fsummary> + <desc> + <p>All applications are taken down smoothly, all code is + unloaded, and all ports are closed before the system + terminates. If the <c>-heart</c> command line flag was given, + the <c>heart</c> program is terminated before the Erlang node + terminates. Refer to <c>heart(3)</c> for more information.</p> + <p>To limit the shutdown time, the time <c>init</c> is allowed + to spend taking down applications, the <c>-shutdown_time</c> + command line flag should be used.</p> + </desc> + </func> + <func> + <name>stop(Status) -> void()</name> + <fsummary>Take down an Erlang node smoothly</fsummary> + <type> + <v>Status = int()>=0 | string()</v> + </type> + <desc> + <p>All applications are taken down smoothly, all code is + unloaded, and all ports are closed before the system + terminates by calling <c>halt(Status)</c>. If the + <c>-heart</c> command line flag was given, the <c>heart</c> + program is terminated before the Erlang node + terminates. Refer to <c>heart(3)</c> for more + information.</p> + <p>To limit the shutdown time, the time <c>init</c> is allowed + to spend taking down applications, the <c>-shutdown_time</c> + command line flag should be used.</p> + </desc> + </func> + </funcs> + + <section> + <marker id="flags"></marker> + <title>Command Line Flags</title> + <warning><p>The support for loading of code from archive files is + experimental. The sole purpose of releasing it before it is ready + is to obtain early feedback. The file format, semantics, + interfaces etc. may be changed in a future release. The + <c>-code_path_choice</c> flag is also experimental.</p></warning> + + <p>The <c>init</c> module interprets the following command line + flags:</p> + + <taglist> + <tag><c>--</c></tag> + <item> + <p>Everything following <c>--</c> up to the next flag is + considered plain arguments and can be retrieved using + <c>get_plain_arguments/0</c>.</p> + </item> + <tag><c>-code_path_choice Choice</c></tag> + <item> + <p>This flag can be set to <c>strict</c> or <c>relaxed</c>. It + controls whether each directory in the code path should be + interpreted strictly as it appears in the <c>boot script</c> or if + <c>init</c> should be more relaxed and try to find a suitable + directory if it can choose from a regular ebin directory and + an ebin directory in an archive file. This flag is particular + useful when you want to elaborate with code loading from + archives without editing the <c>boot script</c>. See <seealso + marker="sasl:script">script(4)</seealso> for more information + about interpretation of boot scripts. The flag does also have + a similar affect on how the code server works. See <seealso + marker="kernel:code">code(3)</seealso>.</p> + + </item> + <tag><c>-eval Expr</c></tag> + <item> + <p>Scans, parses and evaluates an arbitrary expression + <c>Expr</c> during system initialization. If any of these + steps fail (syntax error, parse error or exception during + evaluation), Erlang stops with an error message. Here is an + example that seeds the random number generator:</p> + <pre> +% <input>erl -eval '{X,Y,Z}' = now(), random:seed(X,Y,Z).'</input></pre> + <p>This example uses Erlang as a hexadecimal calculator:</p> + <pre> +% <input>erl -noshell -eval 'R = 16#1F+16#A0, io:format("~.16B~n", [R])' \\</input> +<input>-s erlang halt</input> +BF</pre> + <p>If multiple <c>-eval</c> expressions are specified, they + are evaluated sequentially in the order specified. + <c>-eval</c> expressions are evaluated sequentially with + <c>-s</c> and <c>-run</c> function calls (this also in + the order specified). As with <c>-s</c> and <c>-run</c>, an + evaluation that does not terminate, blocks the system + initialization process.</p> + </item> + <tag><c>-extra</c></tag> + <item> + <p>Everything following <c>-extra</c> is considered plain + arguments and can be retrieved using + <c>get_plain_arguments/0</c>.</p> + </item> + <tag><c>-run Mod [Func [Arg1, Arg2, ...]]</c></tag> + <item> + <p>Evaluates the specified function call during system + initialization. <c>Func</c> defaults to <c>start</c>. If no + arguments are provided, the function is assumed to be of arity + 0. Otherwise it is assumed to be of arity 1, taking the list + <c>[Arg1,Arg2,...]</c> as argument. All arguments are passed + as strings. If an exception is raised, Erlang stops with an + error message.</p> + <p>Example:</p> + <pre> +% <input>erl -run foo -run foo bar -run foo bar baz 1 2</input></pre> + <p>This starts the Erlang runtime system and evaluates + the following functions:</p> + <code type="none"> +foo:start() +foo:bar() +foo:bar(["baz", "1", "2"]).</code> + <p>The functions are executed sequentially in an initialization + process, which then terminates normally and passes control to + the user. This means that a <c>-run</c> call which does not + return will block further processing; to avoid this, use + some variant of <c>spawn</c> in such cases.</p> + </item> + <tag><c>-s Mod [Func [Arg1, Arg2, ...]]</c></tag> + <item> + <p>Evaluates the specified function call during system + initialization. <c>Func</c> defaults to <c>start</c>. If no + arguments are provided, the function is assumed to be of arity + 0. Otherwise it is assumed to be of arity 1, taking the list + <c>[Arg1,Arg2,...]</c> as argument. All arguments are passed + as atoms. If an exception is raised, Erlang stops with an + error message.</p> + <p>Example:</p> + <pre> +% <input>erl -s foo -s foo bar -s foo bar baz 1 2</input></pre> + <p>This starts the Erlang runtime system and evaluates + the following functions:</p> + <code type="none"> +foo:start() +foo:bar() +foo:bar([baz, '1', '2']).</code> + <p>The functions are executed sequentially in an initialization + process, which then terminates normally and passes control to + the user. This means that a <c>-s</c> call which does not + return will block further processing; to avoid this, use + some variant of <c>spawn</c> in such cases.</p> + <p>Due to the limited length of atoms, it is recommended that + <c>-run</c> be used instead.</p> + </item> + </taglist> + </section> + + <section> + <title>Example</title> + <pre> +% <input>erl -- a b -children thomas claire -ages 7 3 -- x y</input> +... + +1> <input>init:get_plain_arguments().</input> +["a","b","x","y"] +2> <input>init:get_argument(children).</input> +{ok,[["thomas","claire"]]} +3> <input>init:get_argument(ages).</input> +{ok, [["7","3"]]} +4> <input>init:get_argument(silly).</input> +error</pre> + </section> + + <section> + <title>SEE ALSO</title> + <p><seealso marker="erl_prim_loader">erl_prim_loader(3)</seealso>, + <seealso marker="kernel:heart">heart(3)</seealso></p> + </section> +</erlref> + |