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<comref>
  <header>
    <copyright>
      <year>1998</year><year>2021</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

          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>start_erl</title>
    <prepared>Patrik Nyblom</prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date>1998-08-05</date>
    <rev></rev>
    <file>start_erl.xml</file>
  </header>
  <com>start_erl</com>
  <comsummary>Start Erlang for embedded systems on Windows systems.</comsummary>
  <description>
    <p>The <c><![CDATA[start_erl]]></c> program is specific to
      Windows NT/2000/XP (and later versions of Windows).
      Although there are programs with the same name on other
      platforms, their functionality is different.</p>

    <p>This program is distributed both in compiled
      form (under &lt;Erlang root&gt;\\erts-&lt;version&gt;\\bin) and
      in source form (under &lt;Erlang root&gt;\\erts-&lt;version&gt;\\src).
      The purpose of the source code is to ease customization of the
      program for local needs, such as cyclic restart
      detection. There is also a "make"-file, written for the
      <c><![CDATA[nmake]]></c> program distributed with Microsoft Visual
      C++. This program can, however, be compiled with
      any Win32 C compiler (possibly with minor modifications).</p>

    <p>This program aids release handling on Windows systems.
      The program is to be called by the
      <c><![CDATA[erlsrv]]></c> program, read up the release data file
      <c>start_erl.data</c>, and start Erlang. Some options to
      <c>start_erl</c> are added and removed by the release handler
      during upgrade with emulator restart (more specifically option
      <c><![CDATA[-data]]></c>).</p>
  </description>

  <funcs>
    <func>
      <name>start_erl [&lt;erl options>] ++ [&lt;start_erl options>]</name>
      <fsummary>Start the Erlang emulator with the correct release data.
      </fsummary>
      <desc>
        <p>The <c><![CDATA[start_erl]]></c> program in its original form
          recognizes the following options:</p>
        <taglist>
          <tag><c>++</c></tag>
          <item>
            <p>Mandatory. Delimits <c>start_erl</c> options from normal Erlang
              options. Everything on the command line <em>before</em>
              <c><![CDATA[++]]></c> is interpreted as options to be sent to the
              <c><![CDATA[erl]]></c> program. Everything <em>after</em>
              <c><![CDATA[++]]></c> is interpreted as options to
              <c><![CDATA[start_erl]]></c> itself.</p>
          </item>
          <tag><c>-reldir &lt;release root&gt;</c></tag>
          <item>
            <p>Mandatory if environment variable
              <c><![CDATA[RELDIR]]></c> is not specified and no
              <c>-rootdir</c> option is specified. Tells <c>start_erl</c> where
              the root of the release tree is located in the file system
              (typically &lt;Erlang root&gt;\\releases). The
              <c><![CDATA[start_erl.data]]></c> file is expected to be
              located in this directory (unless otherwise specified). If
              only option <c>-rootdir</c> is specified, the directory is
              assumed to be &lt;Erlang root&gt;\\releases.</p>
          </item>
          <tag><c>-rootdir &lt;Erlang root directory&gt;</c></tag>
          <item>
            <p>Mandatory if <c>-reldir</c> is not specified and no
              <c><![CDATA[RELDIR]]></c> exists in the environment. This
              specifies the Erlang installation root directory (under
              which the <c>lib</c>, <c>releases</c>, and
              <c>erts-&lt;Version&gt;</c> directories are located). If only
              <c>-reldir</c> (or environment variable <c><![CDATA[RELDIR]]></c>)
              is specified, the Erlang root is assumed to
              be the directory exactly one level above the release
              directory.</p>
          </item>
          <tag><c>-data &lt;data file name&gt;</c></tag>
          <item>
            <p>Optional. Specifies another data file than <c>start_erl.data</c>
              in the &lt;release root&gt;. It is specified relative to the
              &lt;release root&gt; or absolute (including drive letter, and so
              on). This option is used by the release handler during
              upgrade and is not to be used during normal
              operation. Normally the release data file is not to be
              named differently.</p>
          </item>
          <tag><c>-bootflags &lt;boot flags file name&gt;</c></tag>
          <item>
            <p>Optional. Specifies a file name relative to the release
              directory (that is, the subdirectory of &lt;release root&gt;
              where the <c><![CDATA[.boot]]></c> file and others are located).
              The contents of this file is appended to the command line
              when Erlang is started. This makes it easy to start the
              emulator with different options for different releases.</p>
          </item>
        </taglist>
      </desc>
    </func>
  </funcs>

  <section>
    <title>Notes</title>
    <list type="bulleted">
      <item>
        <p>As the source code is distributed, it can easily be modified to
          accept other options. The program must still accept option
          <c><![CDATA[-data]]></c> with the semantics described above for the
          release handler to work correctly.</p>
      </item>
      <item>
        <p>The Erlang emulator is found by examining the registry keys for
          the emulator version specified in the release data file. The new
          emulator must be properly installed before the upgrade for
          this to work.</p>
      </item>
      <item>
        <p>Although the program is located together with files specific to the
          emulator version, it is not expected to be specific to the
          emulator version. The release handler does <em>not</em> change option
          <c><![CDATA[-machine]]></c> to <c><![CDATA[erlsrv]]></c> during
          emulator restart. Locate the (possibly customized)
          <c><![CDATA[start_erl]]></c> program so that it is not overwritten
          during upgrade.</p>
      </item>
      <item>
        <p>The default options of the <c><![CDATA[erlsrv]]></c> program are not
          sufficient for release handling. The machine started by
          <c><![CDATA[erlsrv]]></c> is be specified as the
          <c><![CDATA[start_erl]]></c> program and the arguments are to contain
          <c><![CDATA[++]]></c> followed by the desired options.</p>
      </item>
    </list>
  </section>

  <section>
    <title>See Also</title>
    <p><seecom marker="erlsrv"><c>erlsrv(1)</c></seecom>,
      <seeerl marker="sasl:release_handler">
      <c>release_handler(3)</c></seeerl></p>
  </section>
</comref>
