config(5)							       Files								 config(5)

NAME

       config - Configuration file.

DESCRIPTION

       A configuration file contains values for configuration parameters for the applications in the system. The erl command line argument -config
       Name tells the system to use data in the system configuration file Name.config .

       Configuration parameter values in the configuration file will override the values in the application resource files (see app(5) ). The val-
       ues in the configuration file can be overridden by command line flags (see erl(1) ).

       The value of a configuration parameter is retrieved by calling application:get_env/1,2 .

FILE SYNTAX

       The configuration file should be called Name.config where Name is an arbitrary name.

       The .config file contains one single Erlang term. The file has the following syntax:

       [{Application1, [{Par11, Val11}, ..]},
	..
	{ApplicationN, [{ParN1, ValN1}, ..]}].

	 * Application = atom() is the name of the application.

	 * Par = atom() is the name of a configuration parameter.

	 * Val = term() is the value of a configuration parameter.

SYS.CONFIG
       When  starting  Erlang  in  embedded  mode,  it is assumed that exactly one system configuration file is used, named sys.config . This file
       should be located in $ROOT/releases/Vsn , where $ROOT is the Erlang/OTP root installation directory and Vsn is the release version.

       Release handling relies on this assumption. When installing a new release version, the new sys.config is read and used to update the appli-
       cation configurations.

       This  means  that  specifying another, or additional, .config files would lead to inconsistent update of application configurations. There-
       fore, in Erlang 5.4/OTP R10B, the syntax of sys.config was extended to allow pointing out other .config files:

       [{Application, [{Par, Val}]} | File].

	 * File = string() is the name of another .config file. The extension .config may be omitted. It is recommended to use absolute  paths.  A
	   relative path is relative the current working directory of the emulator.

       When  traversing the contents of sys.config and a filename is encountered, its contents are read and merged with the result so far. When an
       application configuration tuple {Application, Env} is found, it is merged with the result so far. Merging means	that  new  parameters  are
       added and existing parameter values overwritten. Example:

       sys.config:

       [{myapp,[{par1,val1},{par2,val2}]},
	"/home/user/myconfig"].

       myconfig.config:

       [{myapp,[{par2,val3},{par3,val4}]}].

       This will yield the following environment for myapp :

       [{par1,val1},{par2,val3},{par3,val4}]

       The  behaviour  if  a  file specified in sys.config does not exist or is erroneous in some other way, is backwards compatible. Starting the
       runtime system will fail. Installing a new release version will not fail, but an error message is given and the erroneous file is ignored.

SEE ALSO

       app(5) , erl(1) , OTP Design Principles

Ericsson AB							   kernel 2.14.3							 config(5)