init.3erl - Man Page

Code loading mode.

Starts the Erlang runtime system. This function is called when the emulator is started and coordinates system startup.

BootArgs are all command-line arguments except the emulator flags, that is, flags and plain arguments; see erl(1).

init interprets some of the flags, see section Command-Line Flags below. The remaining flags ("user flags") and plain arguments are passed to the init loop and can be retrieved by calling get_arguments/0 and get_plain_arguments/0, respectively.

Returns all values associated with the command-line user flag Flag. If Flag is provided several times, each Values is returned in preserved order. Example:

% erl -a b c -a d
1> init:get_argument(a).
{ok,[["b","c"],["d"]]}

The following flags are defined automatically and can be retrieved using this function:

2> init:get_argument(root).
{ok,[["/usr/local/otp/releases/otp_beam_solaris8_r10b_patched"]]}

3> init:get_argument(progname).
{ok,[["erl"]]}

4> init:get_argument(home).
{ok,[["/home/harry"]]}

Returns error if no value is associated with Flag.

Types:

Flags = [{Flag :: atom(), Values :: [string()]}]

Returns all command-line flags and the system-defined flags, see get_argument/1.

Types:

Arg = string()

Returns any plain command-line arguments as a list of strings (possibly empty).

Types:

InternalStatus = internal_status()
ProvidedStatus = term()

internal_status() = starting | started | stopping

The current status of the init process can be inspected. During system startup (initialization), InternalStatus is starting, and ProvidedStatus indicates how far the boot script has been interpreted. Each {progress, Info} term interpreted in the boot script affects ProvidedStatus, that is, ProvidedStatus gets the value of Info.

All applications are taken down smoothly, all code is unloaded, and all ports are closed before the system terminates. If command-line flag -heart was specified, the heart program tries to reboot the system. For more information, see heart(3).

To limit the shutdown time, the time init is allowed to spend taking down applications, command-line flag -shutdown_time is to be used.

The same as restart([]).

The system is restarted inside the running Erlang node, which means that the emulator is not restarted. All applications are taken down smoothly, all code is unloaded, and all ports are closed before the system is booted again in the same way as initially started.

The same BootArgs are used when restarting the system unless the mode option is given, allowing the code loading mode to be set to either embedded or interactive. All other BootArgs remain the same.

To limit the shutdown time, the time init is allowed to spend taking down applications, command-line flag -shutdown_time is to be used.

Types:

Id = term()

Gets the identity of the boot script used to boot the system. Id can be any Erlang term. In the delivered boot scripts, Id is {Name, Vsn}. Name and Vsn are strings.

The same as stop(0).

All applications are taken down smoothly, all code is unloaded, and all ports are closed before the system terminates by calling halt(Status). If command-line flag -heart was specified, the heart program is terminated before the Erlang node terminates. For more information, see heart(3).

To limit the shutdown time, the time init is allowed to spend taking down applications, command-line flag -shutdown_time is to be used.

--:

Everything following -- up to the next flag is considered plain arguments and can be retrieved using get_plain_arguments/0.

-code_path_choice Choice:

Can be set to strict or relaxed. It controls how each directory in the code path is to be interpreted:

• Strictly as it appears in the boot script, or
• init is to be more relaxed and try to find a suitable directory if it can choose from a regular ebin directory and an ebin directory in an archive file.

This flag is particular useful when you want to elaborate with code loading from archives without editing the boot script. For more information about interpretation of boot scripts, see script(4). The flag has also a similar effect on how the code server works; see code(3).

-epmd_module Module:

Specifies the module to use for registration and lookup of node names. Defaults to erl_epmd.

-eval Expr:

Scans, parses, and evaluates an arbitrary expression Expr during system initialization. If any of these steps fail (syntax error, parse error, or exception during evaluation), Erlang stops with an error message. In the following example Erlang is used as a hexadecimal calculator:

% erl -noshell -eval 'R = 16#1F+16#A0, io:format("~.16B~n", [R])' \\
-s erlang halt
BF

-extra:

Everything following -extra is considered plain arguments and can be retrieved using get_plain_arguments/0.

-run Mod [Func [Arg1, Arg2, ...]]:

Evaluates the specified function call during system initialization. Func defaults to start. If no arguments are provided, the function is assumed to be of arity 0. Otherwise it is assumed to be of arity 1, taking the list [Arg1,Arg2,...] as argument. All arguments are passed as strings. If an exception is raised, Erlang stops with an error message.

Example:

% erl -run foo -run foo bar -run foo bar baz 1 2

foo:start()
foo:bar()
foo:bar(["baz", "1", "2"]).

-s Mod [Func [Arg1, Arg2, ...]]:

Evaluates the specified function call during system initialization. Func defaults to start. If no arguments are provided, the function is assumed to be of arity 0. Otherwise it is assumed to be of arity 1, taking the list [Arg1,Arg2,...] as argument. All arguments are passed as atoms. If an exception is raised, Erlang stops with an error message.

Example:

% erl -s foo -s foo bar -s foo bar baz 1 2

foo:start()
foo:bar()
foo:bar([baz, '1', '2']).