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.TH erl_prim_loader 3 "kernel 2.12.3" "Ericsson AB" "ERLANG MODULE DEFINITION"
.SH MODULE
erl_prim_loader \- Low Level Erlang Loader
.SH DESCRIPTION
.LP
\fIerl_prim_loader\fR is used to load all Erlang modules into the system\&. The start script is also fetched with this low level loader\&.
.LP
\fIerl_prim_loader\fR knows about the environment and how to fetch modules\&. The loader could, for example, fetch files using the file system (with absolute file names as input), or a database (where the binary format of a module is stored)\&.
.LP
The \fI-loader Loader\fR command line flag can be used to choose the method used by the \fIerl_prim_loader\fR\&. Two \fILoader\fR methods are supported by the Erlang runtime system: \fIefile\fR and \fIinet\fR\&. If another loader is required, then it has to be implemented by the user\&. The \fILoader\fR provided by the user must fulfill the protocol defined below, and it is started with the \fIerl_prim_loader\fR by evaluating \fIopen_port({spawn, Loader}, [binary])\fR\&.
.SH EXPORTS
.LP
.B
start(Id, Loader, Hosts) -> {ok, Pid} | {error, What}
.br
.RS
.TP
Types
Id = term()
.br
Loader = atom() | string()
.br
Hosts = [Host]
.br
Host = atom()
.br
Pid = pid()
.br
What = term()
.br
.RE
.RS
.LP
Starts the Erlang low level loader\&. This function is called by the \fIinit\fR process (and module)\&. The \fIinit\fR process reads the command line flags \fI-id Id\fR, \fI-loader Loader\fR, and \fI-hosts Hosts\fR\&. These are the arguments supplied to the \fIstart/3\fR function\&.
.LP
If \fI-loader\fR is not given, the default loader is \fIefile\fR which tells the system to read from the file system\&.
.LP
If \fI-loader\fR is \fIinet\fR, the \fI-id Id\fR, \fI-hosts Hosts\fR, and \fI-setcookie Cookie\fR flags must also be supplied\&. \fIHosts\fR identifies hosts which this node can contact in order to load modules\&. One Erlang runtime system with a \fIerl_boot_server\fR process must be started on each of hosts given in \fIHosts\fR in order to answer the requests\&. See \fIerl_boot_server(3)\fR\&.
.LP
If \fI-loader\fR is something else, the given port program is started\&. The port program is supposed to follow the protocol specified below\&.
.RE
.LP
.B
get_file(File) -> {ok, Bin, FullName} | error
.br
.RS
.TP
Types
File = string()
.br
Bin = binary()
.br
FullName = string()
.br
.RE
.RS
.LP
This function fetches a file using the low level loader\&. \fIFile\fR is either an absolute file name or just the name of the file, for example \fI"lists\&.beam"\fR\&. If an internal path is set to the loader, this path is used to find the file\&. If a user supplied loader is used, the path can be stripped off if it is obsolete, and the loader does not use a path\&. \fIFullName\fR is the complete name of the fetched file\&. \fIBin\fR is the contents of the file as a binary\&.
.RE
.LP
.B
get_path() -> {ok, Path}
.br
.RS
.TP
Types
Path = [Dir]
.br
Dir = string()
.br
.RE
.RS
.LP
This function gets the path set in the loader\&. The path is set by the \fIinit\fR process according to information found in the start script\&.
.RE
.LP
.B
set_path(Path) -> ok
.br
.RS
.TP
Types
Path = [Dir]
.br
Dir = string()
.br
.RE
.RS
.LP
This function sets the path of the loader if \fIinit\fR interprets a \fIpath\fR command in the start script\&.
.RE
.SH PROTOCOL
.LP
The following protocol must be followed if a user provided loader port program is used\&. The \fILoader\fR port program is started with the command \fIopen_port({spawn, Loader}, [binary])\fR\&. The protocol is as follows:
.nf
Function Send Receive
-------------------------------------------------------------
get_file [102 | FileName] [121 | BinaryFile] (on success)
[122] (failure)
stop eof terminate
.fi
.SH COMMAND LINE FLAGS
.LP
The \fIerl_prim_loader\fR module interprets the following command line flags:
.RS 2
.TP 4
.B
\fI-loader Loader\fR:
Specifies the name of the loader used by \fIerl_prim_loader\fR\&. \fILoader\fR can be \fIefile\fR (use the local file system), or \fIinet\fR (load using the \fIboot_server\fR on another Erlang node)\&. If \fILoader\fR is user defined, the defined \fILoader\fR port program is started\&.
.RS 4
.LP
.LP
If the \fI-loader\fR flag is omitted, it defaults to \fIefile\fR\&.
.RE
.TP 4
.B
\fI-hosts Hosts\fR:
Specifies which other Erlang nodes the \fIinet\fR loader can use\&. This flag is mandatory if the \fI-loader inet\fR flag is present\&. On each host, there must be on Erlang node with the \fIerl_boot_server\fR which handles the load requests\&. \fIHosts\fR is a list of IP addresses (hostnames are not acceptable)\&.
.TP 4
.B
\fI-id Id\fR:
Specifies the identity of the Erlang runtime system\&. If the system runs as a distributed node, \fIId\fR must be identical to the name supplied with the \fI-sname\fR or \fI-name\fR distribution flags\&.
.TP 4
.B
\fI-setcookie Cookie\fR:
Specifies the cookie of the Erlang runtime system\&. This flag is mandatory if the \fI-loader inet\fR flag is present\&.
.RE
.SH SEE ALSO
.LP
init(3), erl_boot_server(3)
|
