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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<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
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>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" since="OTP 17.1.2"/>
<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>
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