path: root/erts/doc/src/erl_prim_loader.xml

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<erlref>
  <header>
    <copyright>
      <year>1996</year><year>2016</year>
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      Licensed under the Apache License, Version 2.0 (the "License");
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    <title>erl_prim_loader</title>
    <prepared></prepared>
    <docno></docno>
    <date></date>
    <rev></rev>
    <file>erl_prim_loader.xml</file>
  </header>
  <module>erl_prim_loader</module>
  <modulesummary>Low-level Erlang loader.</modulesummary>
  <description>
    <p>This module is used to load all Erlang modules into
      the system. The start script is also fetched with this low-level
      loader.</p>

    <p><c>erl_prim_loader</c> knows about the environment and how to
      fetch modules.</p>

    <p>Command-line flag <c>-loader Loader</c> can be used to
      choose the method used by <c>erl_prim_loader</c>. Two
      <c>Loader</c> methods are supported by the Erlang runtime system:
      <c>efile</c> and <c>inet</c>.</p>
  </description>

  <funcs>
    <func>
      <name name="get_file" arity="1"/>
      <fsummary>Get a file.</fsummary>
      <desc>
        <p>Fetches a file using the low-level loader.
          <c><anno>Filename</anno></c> is either an absolute filename or only
          the name of the file, for example, <c>"lists.beam"</c>. If an internal
          path is set to the loader, this path is used to find the file.
          <c><anno>FullName</anno></c> is the complete name of the fetched file.
          <c><anno>Bin</anno></c> is the contents of the file as a binary.</p>
        <p><c><anno>Filename</anno></c> can also be a file in an archive,
          for example,
          <c>$OTPROOT/lib/</c><c>mnesia-4.4.7.ez/mnesia-4.4.7/ebin/</c><c>mnesia.beam</c>.
          For information about archive files, see
          <seealso marker="kernel:code"><c>code(3)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="get_path" arity="0"/>
      <fsummary>Get the path set in the loader.</fsummary>
      <desc>
        <p>Gets the path set in the loader. The path is
          set by the <seealso marker="init"><c>init(3)</c></seealso>
          process according to information found in the start script.</p>
      </desc>
    </func>

    <func>
      <name name="list_dir" arity="1"/>
      <fsummary>List files in a directory.</fsummary>
      <desc>
        <p>Lists all the files in a directory. Returns
          <c>{ok, <anno>Filenames</anno>}</c> if successful, otherwise
          <c>error</c>. <c><anno>Filenames</anno></c> is a list of
          the names of all the files in the directory. The names are
          not sorted.</p>
        <p><c><anno>Dir</anno></c> can also be a directory in an archive,
          for example,
          <c>$OTPROOT/lib/</c><c>mnesia-4.4.7.ez/mnesia-4.4.7/ebin</c>.
          For information about archive files, see
          <seealso marker="kernel:code"><c>code(3)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="read_file_info" arity="1"/>
      <fsummary>Get information about a file.</fsummary>
      <desc>
        <p>Retrieves information about a file. Returns
          <c>{ok, <anno>FileInfo</anno>}</c> if successful, otherwise
          <c>error</c>. <c><anno>FileInfo</anno></c> is a record
          <c>file_info</c>, defined in the Kernel include file
          <c>file.hrl</c>. Include the following directive in the module
          from which the function is called:</p>
        <code type="none">
-include_lib("kernel/include/file.hrl").</code>
        <p>For more information about the record <c>file_info</c>, see
          <seealso marker="kernel:file"><c>file(3)</c></seealso>.</p>
        <p><c><anno>Filename</anno></c> can also be a file in an archive,
          for example,
          <c>$OTPROOT/lib/</c><c>mnesia-4.4.7.ez/mnesia-4.4.7/ebin/</c><c>mnesia</c>.
          For information about archive files, see
          <seealso marker="kernel:code"><c>code(3)</c></seealso>.</p>
      </desc>
    </func>

    <func>
      <name name="read_link_info" arity="1"/>
      <fsummary>Get information about a link or file.</fsummary>
      <desc>
        <p>Works like
          <seealso marker="#read_file_info/1"><c>read_file_info/1</c></seealso>
          except that if <c><anno>Filename</anno></c> is a symbolic link,
          information about the link is returned in the <c>file_info</c>
          record and the <c>type</c> field of the record is set to
          <c>symlink</c>.</p>
        <p>If <c><anno>Filename</anno></c> is not a symbolic link, this function
          returns exactly the same result as <c>read_file_info/1</c>.
          On platforms that do not support symbolic links, this function
          is always equivalent to <c>read_file_info/1</c>.</p>
      </desc>
    </func>

    <func>
      <name name="set_path" arity="1"/>
      <fsummary>Set the path of the loader.</fsummary>
      <desc>
        <p>Sets the path of the loader if
          <seealso marker="init"><c>init(3)</c></seealso>
          interprets a <c>path</c> command in the start script.</p>
      </desc>
    </func>
  </funcs>

  <section>
    <title>Command-Line Flags</title>
    <p>The <c>erl_prim_loader</c> module interprets the following
      command-line flags:</p>

    <taglist>
      <tag><c>-loader Loader</c></tag>
      <item>
        <p>Specifies the name of the loader used by
          <c>erl_prim_loader</c>. <c>Loader</c> can be <c>efile</c>
          (use the local file system) or <c>inet</c> (load using
          the <c>boot_server</c> on another Erlang node).</p>
        <p>If flag <c>-loader</c> is omitted, it defaults to
          <c>efile</c>.</p>
      </item>
      <tag><c>-loader_debug</c></tag>
      <item>
          <p>Makes the <c>efile</c> loader write some debug information,
            such as the reason for failures, while it handles files.</p>
      </item>
      <tag><c>-hosts Hosts</c></tag>
      <item>
        <p>Specifies which other Erlang nodes the <c>inet</c> loader
          can use. This flag is mandatory if flag <c>-loader inet</c>
          is present. On each host, there must be on Erlang node
          with the <seealso marker="kernel:erl_boot_server">
          <c>erl_boot_server(3)</c></seealso>,
          which handles the load requests.
          <c>Hosts</c> is a list of IP addresses (hostnames
          are not acceptable).</p>
      </item>
      <tag><c>-setcookie Cookie</c></tag>
      <item>
        <p>Specifies the cookie of the Erlang runtime system. This flag
          is mandatory if flag <c>-loader inet</c> is present.</p>
      </item>
    </taglist>
  </section>

  <section>
    <title>See Also</title>
    <p><seealso marker="init"><c>init(3)</c></seealso>,
      <seealso marker="kernel:erl_boot_server">
      <c>erl_boot_server(3)</c></seealso></p>
  </section>
</erlref>