path: root/lib/erl_interface/doc/src/erl_call.xml

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<comref>
  <header>
    <copyright>
      <year>1996</year><year>2016</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
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      Unless required by applicable law or agreed to in writing, software
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      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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    </legalnotice>

    <title>erl_call</title>
    <prepared>Torbj&ouml;rn T&ouml;rnkvist</prepared>
    <responsible>Torbj&ouml;rn T&ouml;rnkvist</responsible>
    <docno></docno>
    <approved>Bjarne D&auml;cker</approved>
    <checked>Torbj&ouml;rn T&ouml;rnkvist</checked>
    <date>97-05-16</date>
    <rev>B</rev>
    <file>erl_call.sgml</file>
  </header>
  <com>erl_call</com>
  <comsummary>Call/Start a Distributed Erlang Node</comsummary>
  <description>
    <p><c><![CDATA[erl_call]]></c> makes it possible to start and/or communicate with 
      a distributed Erlang node. It is built upon the <c><![CDATA[erl_interface]]></c> 
      library as an example application. Its purpose is to use an Unix shell script to interact with a distributed Erlang node. It performs all 
      communication with the Erlang <em>rex server</em>, using the standard Erlang RPC facility. It does not require any special
      software to be run at the Erlang target node.</p>
    <p>The main use is to either start a distributed Erlang node
      or to make an ordinary function call. However, it is also
      possible to pipe an Erlang module to <c><![CDATA[erl_call]]></c> and have it
      compiled, or to pipe a sequence of Erlang expressions to be evaluated
      (similar to the Erlang shell).</p>
    <p>Options, which cause <c><![CDATA[stdin]]></c> to be read, can be used with
      advantage 
      as scripts from within (Unix) shell scripts. Another 
      nice use of <c><![CDATA[erl_call]]></c> could be from (http) CGI-bin scripts.</p>
  </description>
  <funcs>
    <func>
      <name>erl_call &lt;options></name>
      <fsummary>Start/Call Erlang</fsummary>
      <desc>
        <p>Each option flag is described below with its name, type and
          meaning. </p>
        <taglist>
          <tag>-a [Mod [Fun [Args]]]]</tag>
          <item>
            <p>(<em>optional</em>): Applies the specified function
              and returns the result. <c><![CDATA[Mod]]></c> must be specified, however
              <c>start</c> and <c>[]</c> are assumed for unspecified <c><![CDATA[Fun]]></c> and <c><![CDATA[Args]]></c>, respectively. <c><![CDATA[Args]]></c> should
              be in the same format as for <c><![CDATA[erlang:apply/3]]></c>. Note
              that this flag takes exactly one argument, so quoting
              may be necessary in order to group <c><![CDATA[Mod]]></c>, <c><![CDATA[Fun]]></c>
              and <c><![CDATA[Args]]></c>, in a manner dependent on the behavior
              of your command shell.</p>
            <p></p>
          </item>
          <tag>-c Cookie</tag>
          <item>
            <p>(<em>optional</em>): Use this option to specify a certain cookie. If no cookie is specified, the <c><![CDATA[~/.erlang.cookie]]></c> file is read and its content are used as cookie. The Erlang node we want to communicate with must have the same cookie.</p>
          </item>
          <tag>-d</tag>
          <item>
            <p>(<em>optional</em>): Debug mode. This causes all IO to be output
              to the file <c><![CDATA[~/.erl_call.out.Nodename]]></c>, where <c><![CDATA[Nodename]]></c>
              is the node name of the Erlang node in question.</p>
            <p></p>
          </item>
          <tag>-e</tag>
          <item>
            <p>(<em>optional</em>): Reads a sequence of Erlang expressions, separated
              by '<em>,</em>' and ended with a '<em>.</em>', from <c><![CDATA[stdin]]></c> until
              EOF (Control-D). Evaluates the expressions and returns the result from 
              the last expression. Returns <c><![CDATA[{ok,Result}]]></c> if successful.</p>
            <p></p>
          </item>
          <tag>-h HiddenName</tag>
          <item>
            <p>(<em>optional</em>): Specifies the name of the hidden node
              that <c><![CDATA[erl_call]]></c> represents.</p>
            <p></p>
          </item>
          <tag>-m</tag>
          <item>
            <p>(<em>optional</em>): Reads an Erlang module from <c><![CDATA[stdin]]></c> and
              compiles it.</p>
            <p></p>
          </item>
          <tag>-n Node</tag>
          <item>
            <p>(one of <c><![CDATA[-n, -name, -sname]]></c> is required): 
              Has the same meaning as <c><![CDATA[-name]]></c> and can still be used for 
              backwards compatibility reasons.</p>
            <p></p>
          </item>
          <tag>-name Node</tag>
          <item>
            <p>(one of <c><![CDATA[-n, -name, -sname]]></c> is required): <c><![CDATA[Node]]></c> is the name of the node to be
              started or communicated with. It is assumed that 
              <c><![CDATA[Node]]></c> is started with <c><![CDATA[erl -name]]></c>, which means that fully 
              qualified long node names are used. 
              If the <c><![CDATA[-s]]></c> option is given, an Erlang node will (if necessary) 
              be started with <c><![CDATA[erl -name]]></c>.</p>
            <p></p>
          </item>
          <tag>-q</tag>
          <item>
            <p>(<em>optional</em>): Halts the Erlang node specified
              with the -n switch. This switch overrides the -s switch.</p>
            <p></p>
          </item>
          <tag>-r</tag>
          <item>
            <p>(<em>optional</em>): Generates a random name of the hidden node
              that <c><![CDATA[erl_call]]></c> represents.</p>
            <p></p>
          </item>
          <tag>-s</tag>
          <item>
            <p>(<em>optional</em>): Starts a distributed Erlang node if necessary.
              This means that in a sequence of calls, where the '<c><![CDATA[-s]]></c>'
              and '<c><![CDATA[-n Node]]></c>' are constant, only the first call will start
              the Erlang node. This makes the rest of the communication 
              very fast. This flag is currently only available on the Unix platform.</p>
            <p></p>
          </item>
          <tag>-sname Node</tag>
          <item>
            <p>(one of <c><![CDATA[-n, -name, -sname]]></c> is required): <c><![CDATA[Node]]></c> is the name of the node to
              be started or communicated with. It is assumed that <c><![CDATA[Node]]></c> is started with <c><![CDATA[erl -sname]]></c> which means that short node names are used.
              If <c><![CDATA[-s]]></c> option is given, an Erlang node will be started (if necessary) with <c><![CDATA[erl -sname]]></c>.</p>
            <p></p>
          </item>
          <tag>-v</tag>
          <item>
            <p>(<em>optional</em>): Prints a lot of <c><![CDATA[verbose]]></c> information.
              This is only useful for the developer and maintainer of <c><![CDATA[erl_call]]></c>.</p>
            <p></p>
          </item>
          <tag>-x ErlScript</tag>
          <item>
            <p>(<em>optional</em>): Specifies another name of the Erlang start-up script
              to be used. If not specified, the standard <c><![CDATA[erl]]></c> start-up script
              is used.</p>
          </item>
        </taglist>
      </desc>
    </func>
  </funcs>

  <section>
    <title>Examples</title>
    <p>Starts an Erlang node and calls <c><![CDATA[erlang:time/0]]></c>.</p>
    <code type="none"><![CDATA[
erl_call -s -a 'erlang time' -n madonna
{18,27,34}
    ]]></code>
    <p>Terminates an Erlang node by calling <c><![CDATA[erlang:halt/0]]></c>.</p>
    <code type="none"><![CDATA[
erl_call -s -a 'erlang halt' -n madonna
    ]]></code>
    <p>An apply with several arguments.</p>
    <code type="none"><![CDATA[
erl_call -s -a 'lists map [{math,sqrt},[1,4,9,16,25]]' -n madonna
    ]]></code>
    <p>Evaluates a couple of expressions. <em>The input ends with EOF (Control-D)</em>.</p>
    <code type="none"><![CDATA[
erl_call -s -e -n madonna
statistics(runtime),
X=1,
Y=2,
{_,T}=statistics(runtime),
{X+Y,T}.
^D
{ok,{3,0}}
    ]]></code>
    <p>Compiles a module and runs it. <em>Again, the input ends with EOF (Control-D)</em>. (In the example shown, the output has been formatted afterwards).</p>
    <code type="none"><![CDATA[
erl_call -s -m -a lolita -n madonna
-module(lolita).
-compile(export_all).
start() ->
        P = processes(),
        F = fun(X) -> {X,process_info(X,registered_name)} end,
        lists:map(F,[],P).
^D
[{<[email protected],0,0>,
                  {registered_name,init}},
 {<[email protected],2,0>,
                  {registered_name,erl_prim_loader}},
 {<[email protected],4,0>,
                  {registered_name,error_logger}},
 {<[email protected],5,0>,
                  {registered_name,application_controller}},
 {<[email protected],6,0>,
                  {registered_name,kernel}},
 {<[email protected],7,0>,
                  []},
 {<[email protected],8,0>,
                  {registered_name,kernel_sup}},
 {<[email protected],9,0>,
                  {registered_name,net_sup}},
 {<[email protected],10,0>,
                  {registered_name,net_kernel}},
 {<[email protected],11,0>,
                  []},
 {<[email protected],12,0>,
                  {registered_name,global_name_server}},
 {<[email protected],13,0>,
                  {registered_name,auth}},
 {<[email protected],14,0>,
                  {registered_name,rex}},
 {<[email protected],15,0>,
                  []},
 {<[email protected],16,0>,
                  {registered_name,file_server}},
 {<[email protected],17,0>,
                  {registered_name,code_server}},
 {<[email protected],20,0>,
                  {registered_name,user}},
 {<[email protected],38,0>,
                  []}]
    ]]></code>
  </section>
</comref>