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<!DOCTYPE comref SYSTEM "comref.dtd">

<comref>
  <header>
    <copyright>
      <year>1996</year><year>2010</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>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. <b>The input ends with EOF (Control-D)</b>.</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. <b>Again, the input ends with EOF (Control-D)</b>. (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
[{<madonna@chivas.du.etx.ericsson.se,0,0>,
                  {registered_name,init}},
 {<madonna@chivas.du.etx.ericsson.se,2,0>,
                  {registered_name,erl_prim_loader}},
 {<madonna@chivas.du.etx.ericsson.se,4,0>,
                  {registered_name,error_logger}},
 {<madonna@chivas.du.etx.ericsson.se,5,0>,
                  {registered_name,application_controller}},
 {<madonna@chivas.du.etx.ericsson.se,6,0>,
                  {registered_name,kernel}},
 {<madonna@chivas.du.etx.ericsson.se,7,0>,
                  []},
 {<madonna@chivas.du.etx.ericsson.se,8,0>,
                  {registered_name,kernel_sup}},
 {<madonna@chivas.du.etx.ericsson.se,9,0>,
                  {registered_name,net_sup}},
 {<madonna@chivas.du.etx.ericsson.se,10,0>,
                  {registered_name,net_kernel}},
 {<madonna@chivas.du.etx.ericsson.se,11,0>,
                  []},
 {<madonna@chivas.du.etx.ericsson.se,12,0>,
                  {registered_name,global_name_server}},
 {<madonna@chivas.du.etx.ericsson.se,13,0>,
                  {registered_name,auth}},
 {<madonna@chivas.du.etx.ericsson.se,14,0>,
                  {registered_name,rex}},
 {<madonna@chivas.du.etx.ericsson.se,15,0>,
                  []},
 {<madonna@chivas.du.etx.ericsson.se,16,0>,
                  {registered_name,file_server}},
 {<madonna@chivas.du.etx.ericsson.se,17,0>,
                  {registered_name,code_server}},
 {<madonna@chivas.du.etx.ericsson.se,20,0>,
                  {registered_name,user}},
 {<madonna@chivas.du.etx.ericsson.se,38,0>,
                  []}]
    ]]></code>
  </section>
</comref>

