EVOLUTION-MANAGER

Edit File: init.3

.TH init 3 "erts 5.10.4" "Ericsson AB" "Erlang Module Definition" .SH NAME init \- Coordination of System Startup .SH DESCRIPTION .LP The \fIinit\fR\& module is pre-loaded and contains the code for the \fIinit\fR\& system process which coordinates the start-up of the system\&. The first function evaluated at start-up is \fIboot(BootArgs)\fR\&, where \fIBootArgs\fR\& is a list of command line arguments supplied to the Erlang runtime system from the local operating system\&. See \fBerl(1)\fR\&\&. .LP \fIinit\fR\& reads the boot script which contains instructions on how to initiate the system\&. See \fBscript(4)\fR\& for more information about boot scripts\&. .LP \fIinit\fR\& also contains functions to restart, reboot, and stop the system\&. .SH EXPORTS .LP .nf .B boot(BootArgs) -> no_return() .br .fi .br .RS .LP Types: .RS 3 BootArgs = [binary()] .br .RE .RE .RS .LP Starts the Erlang runtime system\&. This function is called when the emulator is started and coordinates system start-up\&. .LP \fIBootArgs\fR\& are all command line arguments except the emulator flags, that is, flags and plain arguments\&. See \fBerl(1)\fR\&\&. .LP \fIinit\fR\& itself interprets some of the flags, see \fBCommand Line Flags\fR\& below\&. The remaining flags ("user flags") and plain arguments are passed to the \fIinit\fR\& loop and can be retrieved by calling \fIget_arguments/0\fR\& and \fIget_plain_arguments/0\fR\&, respectively\&. .RE .LP .nf .B get_argument(Flag) -> {ok, Arg} | error .br .fi .br .RS .LP Types: .RS 3 Flag = atom() .br Arg = [Values :: [string()]] .br .RE .RE .RS .LP Returns all values associated with the command line user flag \fIFlag\fR\&\&. If \fIFlag\fR\& is provided several times, each \fIValues\fR\& is returned in preserved order\&. .LP .nf % erl -a b c -a d ... 1> init:get_argument(a)\&. {ok,[["b","c"],["d"]]} .fi .LP There are also a number of flags, which are defined automatically and can be retrieved using this function: .RS 2 .TP 2 .B \fIroot\fR\&: The installation directory of Erlang/OTP, \fI$ROOT\fR\&\&. .LP .nf 2> init:get_argument(root)\&. {ok,[["/usr/local/otp/releases/otp_beam_solaris8_r10b_patched"]]} .fi .TP 2 .B \fIprogname\fR\&: The name of the program which started Erlang\&. .LP .nf 3> init:get_argument(progname)\&. {ok,[["erl"]]} .fi .TP 2 .B \fIhome\fR\&: The home directory\&. .LP .nf 4> init:get_argument(home)\&. {ok,[["/home/harry"]]} .fi .RE .LP Returns \fIerror\fR\& if there is no value associated with \fIFlag\fR\&\&. .RE .LP .nf .B get_arguments() -> Flags .br .fi .br .RS .LP Types: .RS 3 Flags = [{Flag :: atom(), Values :: [string()]}] .br .RE .RE .RS .LP Returns all command line flags, as well as the system defined flags, see \fIget_argument/1\fR\&\&. .RE .LP .nf .B get_plain_arguments() -> [Arg] .br .fi .br .RS .LP Types: .RS 3 Arg = string() .br .RE .RE .RS .LP Returns any plain command line arguments as a list of strings (possibly empty)\&. .RE .LP .nf .B get_status() -> {InternalStatus, ProvidedStatus} .br .fi .br .RS .LP Types: .RS 3 InternalStatus = \fBinternal_status()\fR\& .br ProvidedStatus = term() .br .nf \fBinternal_status()\fR\& = starting | started | stopping .fi .br .RE .RE .RS .LP The current status of the \fIinit\fR\& process can be inspected\&. During system startup (initialization), \fIInternalStatus\fR\& is \fIstarting\fR\&, and \fIProvidedStatus\fR\& indicates how far the boot script has been interpreted\&. Each \fI{progress, Info}\fR\& term interpreted in the boot script affects \fIProvidedStatus\fR\&, that is, \fIProvidedStatus\fR\& gets the value of \fIInfo\fR\&\&. .RE .LP .nf .B reboot() -> ok .br .fi .br .RS .LP All applications are taken down smoothly, all code is unloaded, and all ports are closed before the system terminates\&. If the \fI-heart\fR\& command line flag was given, the \fIheart\fR\& program will try to reboot the system\&. Refer to \fIheart(3)\fR\& for more information\&. .LP To limit the shutdown time, the time \fIinit\fR\& is allowed to spend taking down applications, the \fI-shutdown_time\fR\& command line flag should be used\&. .RE .LP .nf .B restart() -> ok .br .fi .br .RS .LP The system is restarted \fIinside\fR\& 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 \fIBootArgs\fR\& are used again\&. .LP To limit the shutdown time, the time \fIinit\fR\& is allowed to spend taking down applications, the \fI-shutdown_time\fR\& command line flag should be used\&. .RE .LP .nf .B script_id() -> Id .br .fi .br .RS .LP Types: .RS 3 Id = term() .br .RE .RE .RS .LP Get the identity of the boot script used to boot the system\&. \fIId\fR\& can be any Erlang term\&. In the delivered boot scripts, \fIId\fR\& is \fI{Name, Vsn}\fR\&\&. \fIName\fR\& and \fIVsn\fR\& are strings\&. .RE .LP .nf .B stop() -> ok .br .fi .br .RS .LP All applications are taken down smoothly, all code is unloaded, and all ports are closed before the system terminates\&. If the \fI-heart\fR\& command line flag was given, the \fIheart\fR\& program is terminated before the Erlang node terminates\&. Refer to \fIheart(3)\fR\& for more information\&. .LP To limit the shutdown time, the time \fIinit\fR\& is allowed to spend taking down applications, the \fI-shutdown_time\fR\& command line flag should be used\&. .RE .LP .nf .B stop(Status) -> ok .br .fi .br .RS .LP Types: .RS 3 Status = integer() >= 0 | string() .br .RE .RE .RS .LP All applications are taken down smoothly, all code is unloaded, and all ports are closed before the system terminates by calling \fIhalt(Status)\fR\&\&. If the \fI-heart\fR\& command line flag was given, the \fIheart\fR\& program is terminated before the Erlang node terminates\&. Refer to \fIheart(3)\fR\& for more information\&. .LP To limit the shutdown time, the time \fIinit\fR\& is allowed to spend taking down applications, the \fI-shutdown_time\fR\& command line flag should be used\&. .RE .SH "COMMAND LINE FLAGS" .LP .RS -4 .B Warning: .RE The support for loading of code from archive files is experimental\&. The sole purpose of releasing it before it is ready is to obtain early feedback\&. The file format, semantics, interfaces etc\&. may be changed in a future release\&. The \fI-code_path_choice\fR\& flag is also experimental\&. .LP The \fIinit\fR\& module interprets the following command line flags: .RS 2 .TP 2 .B \fI--\fR\&: Everything following \fI--\fR\& up to the next flag is considered plain arguments and can be retrieved using \fIget_plain_arguments/0\fR\&\&. .TP 2 .B \fI-code_path_choice Choice\fR\&: This flag can be set to \fIstrict\fR\& or \fIrelaxed\fR\&\&. It controls whether each directory in the code path should be interpreted strictly as it appears in the \fIboot script\fR\& or if \fIinit\fR\& should 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 \fIboot script\fR\&\&. See \fBscript(4)\fR\& for more information about interpretation of boot scripts\&. The flag does also have a similar affect on how the code server works\&. See \fBcode(3)\fR\&\&. .TP 2 .B \fI-eval Expr\fR\&: Scans, parses and evaluates an arbitrary expression \fIExpr\fR\& during system initialization\&. If any of these steps fail (syntax error, parse error or exception during evaluation), Erlang stops with an error message\&. Here is an example that seeds the random number generator: .LP .nf % erl -eval \&'{X,Y,Z}\&' = now(), random:seed(X,Y,Z)\&.\&' .fi .RS 2 .LP This example uses Erlang as a hexadecimal calculator: .RE .LP .nf % erl -noshell -eval \&'R = 16#1F+16#A0, io:format("~\&.16B~n", [R])\&' \\\\ -s erlang halt BF .fi .RS 2 .LP If multiple \fI-eval\fR\& expressions are specified, they are evaluated sequentially in the order specified\&. \fI-eval\fR\& expressions are evaluated sequentially with \fI-s\fR\& and \fI-run\fR\& function calls (this also in the order specified)\&. As with \fI-s\fR\& and \fI-run\fR\&, an evaluation that does not terminate, blocks the system initialization process\&. .RE .TP 2 .B \fI-extra\fR\&: Everything following \fI-extra\fR\& is considered plain arguments and can be retrieved using \fIget_plain_arguments/0\fR\&\&. .TP 2 .B \fI-run Mod [Func [Arg1, Arg2, \&.\&.\&.]]\fR\&: Evaluates the specified function call during system initialization\&. \fIFunc\fR\& defaults to \fIstart\fR\&\&. 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 \fI[Arg1,Arg2,\&.\&.\&.]\fR\& as argument\&. All arguments are passed as strings\&. If an exception is raised, Erlang stops with an error message\&. .RS 2 .LP Example: .RE .LP .nf % erl -run foo -run foo bar -run foo bar baz 1 2 .fi .RS 2 .LP This starts the Erlang runtime system and evaluates the following functions: .RE .LP .nf foo:start() foo:bar() foo:bar(["baz", "1", "2"]). .fi .RS 2 .LP The functions are executed sequentially in an initialization process, which then terminates normally and passes control to the user\&. This means that a \fI-run\fR\& call which does not return will block further processing; to avoid this, use some variant of \fIspawn\fR\& in such cases\&. .RE .TP 2 .B \fI-s Mod [Func [Arg1, Arg2, \&.\&.\&.]]\fR\&: Evaluates the specified function call during system initialization\&. \fIFunc\fR\& defaults to \fIstart\fR\&\&. 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 \fI[Arg1,Arg2,\&.\&.\&.]\fR\& as argument\&. All arguments are passed as atoms\&. If an exception is raised, Erlang stops with an error message\&. .RS 2 .LP Example: .RE .LP .nf % erl -s foo -s foo bar -s foo bar baz 1 2 .fi .RS 2 .LP This starts the Erlang runtime system and evaluates the following functions: .RE .LP .nf foo:start() foo:bar() foo:bar([baz, '1', '2']). .fi .RS 2 .LP The functions are executed sequentially in an initialization process, which then terminates normally and passes control to the user\&. This means that a \fI-s\fR\& call which does not return will block further processing; to avoid this, use some variant of \fIspawn\fR\& in such cases\&. .RE .RS 2 .LP Due to the limited length of atoms, it is recommended that \fI-run\fR\& be used instead\&. .RE .RE .SH "EXAMPLE" .LP .nf % erl -- a b -children thomas claire -ages 7 3 -- x y ... 1> init:get_plain_arguments()\&. ["a","b","x","y"] 2> init:get_argument(children)\&. {ok,[["thomas","claire"]]} 3> init:get_argument(ages)\&. {ok, [["7","3"]]} 4> init:get_argument(silly)\&. error .fi .SH "SEE ALSO" .LP \fBerl_prim_loader(3)\fR\&, \fBheart(3)\fR\&