Erlang Run-Time System Application (ERTS)

Reference Manual


Table of Contents




Module Summary

Low-level Erlang loader.


This module is used to load all Erlang modules into the system. The start script is also fetched with this low-level loader.

erl_prim_loader knows about the environment and how to fetch modules.

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

get_file(Filename) -> {ok, Bin, FullName} | error


Filename = atom() | string()
Bin = binary()
FullName = string()

Fetches a file using the low-level loader. Filename is either an absolute filename or only the name of the file, for example, "lists.beam". If an internal path is set to the loader, this path is used to find the file. FullName is the complete name of the fetched file. Bin is the contents of the file as a binary.

Filename can also be a file in an archive, for example, $OTPROOT/lib/mnesia-4.4.7.ez/mnesia-4.4.7/ebin/mnesia.beam. For information about archive files, see code(3).

get_path() -> {ok, Path}


Path = [Dir :: string()]

Gets the path set in the loader. The path is set by the init(3) process according to information found in the start script.

list_dir(Dir) -> {ok, Filenames} | error


Dir = string()
Filenames = [Filename :: string()]

Lists all the files in a directory. Returns {ok, Filenames} if successful, otherwise error. Filenames is a list of the names of all the files in the directory. The names are not sorted.

Dir can also be a directory in an archive, for example, $OTPROOT/lib/mnesia-4.4.7.ez/mnesia-4.4.7/ebin. For information about archive files, see code(3).

read_file_info(Filename) -> {ok, FileInfo} | error


Filename = string()
FileInfo = file:file_info()

Retrieves information about a file. Returns {ok, FileInfo} if successful, otherwise error. FileInfo is a record file_info, defined in the Kernel include file file.hrl. Include the following directive in the module from which the function is called:


For more information about the record file_info, see file(3).

Filename can also be a file in an archive, for example, $OTPROOT/lib/mnesia-4.4.7.ez/mnesia-4.4.7/ebin/mnesia. For information about archive files, see code(3).

read_link_info(Filename) -> {ok, FileInfo} | error
OTP 17.1.2


Filename = string()
FileInfo = file:file_info()

Works like read_file_info/1 except that if Filename is a symbolic link, information about the link is returned in the file_info record and the type field of the record is set to symlink.

If Filename is not a symbolic link, this function returns exactly the same result as read_file_info/1. On platforms that do not support symbolic links, this function is always equivalent to read_file_info/1.

set_path(Path) -> ok


Path = [Dir :: string()]

Sets the path of the loader if init(3) interprets a path command in the start script.

Command-Line Flags

The erl_prim_loader module interprets the following command-line flags:

-loader Loader

Specifies the name of the loader used by erl_prim_loader. Loader can be efile (use the local file system) or inet (load using the boot_server on another Erlang node).

If flag -loader is omitted, it defaults to efile.


Makes the efile loader write some debug information, such as the reason for failures, while it handles files.

-hosts Hosts

Specifies which other Erlang nodes the inet loader can use. This flag is mandatory if flag -loader inet is present. On each host, there must be on Erlang node with the erl_boot_server(3), which handles the load requests. Hosts is a list of IP addresses (hostnames are not acceptable).

-setcookie Cookie

Specifies the cookie of the Erlang runtime system. This flag is mandatory if flag -loader inet is present.