Provided by:
erlang-manpages_14.b.4-dfsg-1ubuntu1_all 
NAME
app - Application resource file.
DESCRIPTION
The application resource file specifies the resources an application
uses, and how the application is started. There must always be one
application resource file called Application.app for each application
Application in the system.
The file is read by the application controller when an application is
loaded/started. It is also used by the functions in systools, for
example when generating start scripts.
FILE SYNTAX
The application resource file should be called Application.app where
Application is the name of the application. The file should be located
in the ebin directory for the application.
It must contain one single Erlang term, which is called an application
specification:
{application, Application,
[{description, Description},
{id, Id},
{vsn, Vsn},
{modules, Modules},
{maxP, MaxP},
{maxT, MaxT},
{registered, Names},
{included_applications, Apps},
{applications, Apps},
{env, Env},
{mod, Start},
{start_phases, Phases}]}.
Value Default
----- -------
Application atom() -
Description string() ""
Id string() ""
Vsn string() ""
Modules [Module] []
MaxP int() infinity
MaxT int() infinity
Names [Name] []
Apps [App] []
Env [{Par,Val}] []
Start {Module,StartArgs} undefined
Phases [{Phase,PhaseArgs}] undefined
Module = Name = App = Par = Phase = atom()
Val = StartArgs = PhaseArgs = term()
Application is the name of the application.
For the application controller, all keys are optional. The respective
default values are used for any omitted keys.
The functions in systools require more information. If they are used,
the following keys are mandatory: description, vsn, modules, registered
and applications. The other keys are ignored by systools.
description:
A one-line description of the application.
id:
Product identification, or similar.
vsn:
The version of the application.
modules:
All modules introduced by this application. systools uses this list
when generating start scripts and tar files. A module can only be
defined in one application.
maxP:
Deprecated - will be ignored
The maximum number of processes allowed in the application.
maxT:
The maximum time in milliseconds that the application is allowed to
run. After the specified time the application will automatically
terminate.
registered:
All names of registered processes started in this application.
systools uses this list to detect name clashes between different
applications.
included_applications:
All applications which are included by this application. When this
application is started, all included application will automatically
be loaded, but not started, by the application controller. It is
assumed that the topmost supervisor of the included application is
started by a supervisor of this application.
applications:
All applications which must be started before this application is
allowed to be started. systools uses this list to generate correct
start scripts. Defaults to the empty list, but note that all
applications have dependencies to (at least) kernel and stdlib.
env:
Configuration parameters used by the application. The value of a
configuration parameter is retrieved by calling
application:get_env/1,2. The values in the application resource
file can be overridden by values in a configuration file (see
config(5)) or by command line flags (see erl(1)).
mod:
Specifies the application callback module and a start argument, see
application(3erl).
The mod key is necessary for an application implemented as a
supervision tree, or the application controller will not know how
to start it. The mod key can be omitted for applications without
processes, typically code libraries such as the application STDLIB.
start_phases:
A list of start phases and corresponding start arguments for the
application. If this key is present, the application master will -
in addition to the usual call to Module:start/2 - also call
Module:start_phase(Phase,Type,PhaseArgs) for each start phase
defined by the start_phases key, and only after this extended start
procedure will application:start(Application) return.
Start phases may be used to synchronize startup of an application
and its included applications. In this case, the mod key must be
specified as:
{mod, {application_starter,[Module,StartArgs]}}
The application master will then call Module:start/2 for the
primary application, followed by calls to Module:start_phase/3 for
each start phase (as defined for the primary application) both for
the primary application and for each of its included application,
for which the start phase is defined.
This implies that for an included application, the set of start
phases must be a subset of the set of phases defined for the
primary application. Refer to OTP Design Principles for more
information.
SEE ALSO
application(3erl), systools(3erl)