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<H1>proc_lib</H1>
</CENTER>
<H3>MODULE</H3>
<DIV CLASS=REFBODY>
proc_lib
</DIV>
<H3>MODULE SUMMARY</H3>
<DIV CLASS=REFBODY>
Plug-in Replacements for spawn/1,2,3,4,
spawn_link/1,2,3,4, and spawn_opt/2,3,4,5.
</DIV>
<H3>DESCRIPTION</H3>
<DIV CLASS=REFBODY>
<P>The <CODE>proc_lib</CODE> module is used to initialize some useful
information when a process starts. The registered names, or the
process identities, of the <CODE>parent</CODE> process, and the parent
ancestors, are stored together with information about the
function initially called in the process.
<P>A crash report is generated if the process terminates with
a reason other than <CODE>normal</CODE> or <CODE>shutdown</CODE>.
<CODE>shutdown</CODE> is used to terminate an abnormal process in a
controlled manner. A crash report contains the previously stored
information such as ancestors and initial function, the
termination reason, and information regarding other processes
which terminate as a result of this process terminating.
<P>The crash report is sent to the <CODE>error_logger</CODE>. An event
handler has to be installed in the <CODE>error_logger</CODE> event
manager in order to handle these reports. The crash report is
tagged <CODE>crash_report</CODE> and the <CODE>format/1</CODE> function
should be called in order to format the report.
</DIV>
<H3>EXPORTS</H3>
<P><A NAME="spawn/1"><STRONG><CODE>spawn(Fun) -> Pid</CODE></STRONG></A><BR>
<A NAME="spawn/2"><STRONG><CODE>spawn(Node,Fun) -> Pid</CODE></STRONG></A><BR>
<A NAME="spawn/3"><STRONG><CODE>spawn(Module,Func,Args) -> Pid</CODE></STRONG></A><BR>
<A NAME="spawn/4"><STRONG><CODE>spawn(Node,Module,Func,Args) -> Pid</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Fun = fun() -> void()</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Func = atom()</CODE></STRONG><BR>
<STRONG><CODE>Args = [Arg]</CODE></STRONG><BR>
<STRONG><CODE>Arg = term()</CODE></STRONG><BR>
<STRONG><CODE>Node = atom()</CODE></STRONG><BR>
<STRONG><CODE>Pid = pid()</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>Spawns a new process and initializes it as described above.
The process is spawned using the <CODE>spawn</CODE> BIFs. The
process can be spawned on another <CODE>Node</CODE>.
</DIV>
<P><A NAME="spawn_link/1"><STRONG><CODE>spawn_link(Fun) -> Pid</CODE></STRONG></A><BR>
<A NAME="spawn_link/2"><STRONG><CODE>spawn_link(Node,Fun) -> Pid</CODE></STRONG></A><BR>
<A NAME="spawn_link/3"><STRONG><CODE>spawn_link(Module,Func,Args) -> Pid</CODE></STRONG></A><BR>
<A NAME="spawn_link/4"><STRONG><CODE>spawn_link(Node,Module,Func,Args) -> Pid</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Fun = fun() -> void()</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Func = atom()</CODE></STRONG><BR>
<STRONG><CODE>Args = [Arg]</CODE></STRONG><BR>
<STRONG><CODE>Arg = term()</CODE></STRONG><BR>
<STRONG><CODE>Node = atom()</CODE></STRONG><BR>
<STRONG><CODE>Pid = pid()</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>Spawns a new process and initializes it as described above.
The process is spawned using the <CODE>spawn_link</CODE> BIFs.
The process can be spawned on another <CODE>Node</CODE>.
</DIV>
<P><A NAME="spawn_opt/2"><STRONG><CODE>spawn_opt(Fun,Opts) -> Pid</CODE></STRONG></A><BR>
<A NAME="spawn_opt/3"><STRONG><CODE>spawn_opt(Node,Fun,Opts) -> Pid</CODE></STRONG></A><BR>
<A NAME="spawn_opt/4"><STRONG><CODE>spawn_opt(Module,Func,Args,Opts) -> Pid</CODE></STRONG></A><BR>
<A NAME="spawn_opt/5"><STRONG><CODE>spawn_opt(Node,Module,Func,Args,Opts) -> Pid</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Fun = fun() -> void()</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Func = atom()</CODE></STRONG><BR>
<STRONG><CODE>Args = [Arg]</CODE></STRONG><BR>
<STRONG><CODE>Arg = term()</CODE></STRONG><BR>
<STRONG><CODE>Node = atom()</CODE></STRONG><BR>
<STRONG><CODE>Opts = list()</CODE></STRONG><BR>
<STRONG><CODE>Pid = pid()</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>Spawns a new process and initializes it as described above.
The process is spawned using the <CODE>spawn_opt</CODE> BIFs. The
process can be spawned on another <CODE>Node</CODE>.
</DIV>
<P><A NAME="start/3"><STRONG><CODE>start(Module,Func,Args) -> Ret</CODE></STRONG></A><BR>
<A NAME="start/4"><STRONG><CODE>start(Module,Func,Args,Time) -> Ret</CODE></STRONG></A><BR>
<A NAME="start/5"><STRONG><CODE>start(Module,Func,Args,Time,SpawnOpts) -> Ret</CODE></STRONG></A><BR>
<A NAME="start_link/3"><STRONG><CODE>start_link(Module,Func,Args) -> Ret</CODE></STRONG></A><BR>
<A NAME="start_link/4"><STRONG><CODE>start_link(Module,Func,Args,Time) -> Ret</CODE></STRONG></A><BR>
<A NAME="start_link/5"><STRONG><CODE>start_link(Module,Func,Args,Time,SpawnOpts) -> Ret</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Func = atom()</CODE></STRONG><BR>
<STRONG><CODE>Args = [Arg]</CODE></STRONG><BR>
<STRONG><CODE>Arg = term()</CODE></STRONG><BR>
<STRONG><CODE>Time = integer >= 0 | infinity</CODE></STRONG><BR>
<STRONG><CODE>SpawnOpts = list()</CODE></STRONG><BR>
<STRONG><CODE>Ret = term() | {error, Reason}</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>Starts a new process synchronously. Spawns the process
using <CODE>proc_lib:spawn/3</CODE> or
<CODE>proc_lib:spawn_link/3</CODE>, and waits for the process to
start. When the process has started, it <STRONG>must</STRONG> call
<CODE>proc_lib:init_ack(Parent, Ret)</CODE> or
<CODE>proc_lib:init_ack(Ret)</CODE>, where <CODE>Parent</CODE>
is the process that evaluates <CODE>start</CODE>. At this time,
<CODE>Ret</CODE> is returned from <CODE>start</CODE>.
<P>If the <CODE>start_link</CODE> function is used and the
process crashes before <CODE>proc_lib:init_ack</CODE> is called,
<CODE>{error, Reason}</CODE> is returned if the calling process
traps exits.
<P>If <CODE>Time</CODE> is specified as an integer, this function
waits for <CODE>Time</CODE> milliseconds for the process to start
(<CODE>proc_lib:init_ack</CODE>). If it has not
started within this time, <CODE>{error, timeout}</CODE> is
returned, and the process is killed.
<P>The <CODE>SpawnOpts</CODE> argument, if given, will be passed
as the last argument to the <CODE>spawn_opt/4</CODE> BIF. Refer to
the <CODE>erlang</CODE> module for information about the
<CODE>spawn_opt</CODE> options.
</DIV>
<P><A NAME="init_ack/2"><STRONG><CODE>init_ack(Parent, Ret) -> void()</CODE></STRONG></A><BR>
<A NAME="init_ack/1"><STRONG><CODE>init_ack(Ret) -> void()</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Parent = pid()</CODE></STRONG><BR>
<STRONG><CODE>Ret = term()</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>This function is used by a process that has been started by
a <CODE>proc_lib:start</CODE> function. It tells <CODE>Parent</CODE>
that the process has initialized itself, has started, or has
failed to initialize itself. The <CODE>init_ack/1</CODE> function
uses the parent value previously stored by the
<CODE>proc_lib:start</CODE> function. If the <CODE>init_ack</CODE>
function is not called (e.g. if the init function crashes)
and <CODE>proc_lib:start/3</CODE> is used, that function never
returns and the parent hangs forever. This can be avoided by
using a time out in the call to <CODE>start</CODE>, or by using
<CODE>start_link</CODE>.
<P>The following example illustrates how this function and
<CODE>proc_lib:start_link</CODE> are used.
<PRE>
-module(my_proc).
-export([start_link/0]).
start_link() ->
proc_lib:start_link(my_proc, init, [self()]).
init(Parent) ->
case do_initialization() of
ok ->
proc_lib:init_ack(Parent, {ok, self()});
{error, Reason} ->
exit(Reason)
end,
loop().
loop() ->
receive
....
</PRE>
</DIV>
<P><A NAME="format/1"><STRONG><CODE>format(CrashReport) -> string()</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>CrashReport = void()</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>Formats a previously generated crash report. The formatted
report is returned as a string.
</DIV>
<P><A NAME="initial_call/1"><STRONG><CODE>initial_call(PidOrPinfo) -> {Module,Function,Args} | Fun | false
</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>PidOrPinfo = pid() | {X,Y,Z} | ProcInfo</CODE></STRONG><BR>
<STRONG><CODE>X = Y = Z = int()</CODE></STRONG><BR>
<STRONG><CODE>ProcInfo = [void()]</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Fun = fun() -> void()</CODE></STRONG><BR>
<STRONG><CODE>Function = atom()</CODE></STRONG><BR>
<STRONG><CODE>Args = [term()]</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>Extracts the initial call of a process that was spawned
using the spawn functions described above. <CODE>PidOrPinfo</CODE>
can either be a Pid, an integer tuple (from which a pid can
be created), or the process information of a process
(fetched through an <CODE>erlang:process_info/1</CODE> function
call).
</DIV>
<P><A NAME="translate_initial_call/1"><STRONG><CODE>translate_initial_call(PidOrPinfo) ->
{Module,Function,Arity} | Fun</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>PidOrPinfo = pid() | {X,Y,Z} | ProcInfo</CODE></STRONG><BR>
<STRONG><CODE>X = Y = Z = int()</CODE></STRONG><BR>
<STRONG><CODE>ProcInfo = [void()]</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Fun = fun() -> void()</CODE></STRONG><BR>
<STRONG><CODE>Function = atom()</CODE></STRONG><BR>
<STRONG><CODE>Arity = int()</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>Extracts the initial call of a process which was spawned
using the spawn functions described above. If the initial
call is to one of the system defined behaviours such as
<CODE>gen_server</CODE> or <CODE>gen_event</CODE>, it is translated to
more useful information. If a <CODE>gen_server</CODE> is spawned,
the returned <CODE>Module</CODE> is the name of the callback
module and <CODE>Function</CODE> is <CODE>init</CODE> (the function that
initiates the new server).
<P>A <CODE>supervisor</CODE> and a <CODE>supervisor_bridge</CODE> are also
<CODE>gen_server</CODE> processes. In order to return information
that this process is a supervisor and the name of the
call-back module, <CODE>Module</CODE> is <CODE>supervisor</CODE> and
<CODE>Function</CODE> is the name of the supervisor callback
module. <CODE>Arity</CODE> is <CODE>1</CODE> since the <CODE>init/1</CODE>
function is called initially in the callback module.
<P>By default, <CODE>{proc_lib,init_p,5}</CODE> is returned if no
information about the initial call can be found. It is
assumed that the caller knows that the process has been
spawned with the <CODE>proc_lib</CODE> module.
<P><CODE>PidOrPinfo</CODE> can either be a Pid, an integer tuple
(from which a pid can be created), or the process
information of a process (fetched through an
<CODE>erlang:process_info/1</CODE> function call).
<P>This function is used by the c:i/0 and c:regs/0 functions
in order to present process information.
</DIV>
<P><A NAME="hibernate/3"><STRONG><CODE>hibernate(Module, Function, Arguments)</CODE></STRONG></A><BR>
<DIV CLASS=REFBODY><P>Types:
<DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Function = atom()</CODE></STRONG><BR>
<STRONG><CODE>Arguments = [term()]</CODE></STRONG><BR>
</DIV>
</DIV>
<DIV CLASS=REFBODY>
<P>
<P><CODE>hibernate/3</CODE> gives a way to put a process started
using one of the functions in the <CODE>proc_lib</CODE> module into
a wait state where its memory allocation has been reduced as much
as possible, which is useful if the process does not expect to
receive any messages in the near future.
<P>The process will be awaken when a message is sent to it, and
control will resume in <CODE>Module:Function</CODE> with the arguments
given by <CODE>ArgumentList</CODE>.
<P>If the process has any message in its message queue, the process
will be awaken immediately in the same way as described above.
<P>Note: The actual work is done by the <CODE>erlang:hibernate/3</CODE> BIF.
To ensure that exception handling and logging continues to work in
a process started by <CODE>proc_lib</CODE>, always use <CODE>proc_lib:hibernate</CODE>
rather than <CODE>erlang:hibernate/3</CODE>.
</DIV>
<H3>See Also</H3>
<DIV CLASS=REFBODY>
<P>error_logger(3)
</DIV>
<H3>AUTHORS</H3>
<DIV CLASS=REFBODY>
Magnus Frberg - support@erlang.ericsson.se<BR>
</DIV>
<CENTER>
<HR>
<SMALL>stdlib 1.14.2<BR>
Copyright © 1991-2006
<A HREF="http://www.erlang.se">Ericsson AB</A><BR>
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