File of configuration

In Data-processing, a file of configuration contains information of configuration used by a Computer program to adapt or personalize its operation.

Definition

The files of configuration are used to impose certain adjustments (parameters of posting, preferences of language, transmission speed and Communication protocols, taken into account of some peripheral, etc) in the applications of the users, the services of a data-processing Serveur, or the Operating systems.

According to the case, the programs read these files only once, at the time of their launching, or check their information periodically in order to detect changes there. It is sometimes possible to announce a modification to the program during its execution: this one it will read again the file of configuration then and will apply the new adjustments instantaneously.

Structure

The structure of the files of configuration is variable: it can conform to the conventions installation by the editor of the operating system, to depend on the development tools used to program an application or to be entirely owner, which makes it often difficult to interpret.

Most of the files of configuration nevertheless is written with the format ASCII (in textual form) and is formatted in lines finished by characters " news ligne" or " CR/LF" ( carriage return/line feed ) according to the operating system. Their contents can then be examined using a text editor.

In other cases, it is necessary to resort to special applications to create, modify and test the syntax of the files of configuration. For the services and the operating systems, the Source code is sometimes only documentation available. In general, the pages of handbook or assistance account partially for syntax to be used in these files.

The formats XML and YAML tend to spread in the writing of the files of configuration. They have the advantage of having a syntax already well defined and of having tools of known checking and validation.

Syntax

For more clearness, the files of configuration in general respect a syntax which associates directives (or words key) with values.

This syntax can adopt forms and levels of complexity different according to the width and the precision from the functionalities of the application.

The parameters can be organized linearly (e.g. rs_vitesse=9600), in table (like fstab) or in " objets" , which is the case with the XML, delimited by a beginning and an end, and characterized by specific properties and options to each type of object.

With the manner of the computer programming languages, the files of configuration can be accompanied by comments which will be ignored by the program, but which will allow to the creators software to insert indications, and with the users to better include/understand the behavior of the program and to neutralize temporarily certain lines.

Types of fichers of configuration

Under UNIX

Among the alternatives of UNIX, there exist hundreds of different formats of file, each application or service having its own format. Historically, the options of the operating system could be modified only by publishing these files, generally in text mode.

The majority of the formats used make it possible to neutralize a line by making it precede by a special character (often #). Such a line is known as " in commentaire". The applications UNIX user often create a file or a repertory of configuration in the personal repertory " home". Their name is preceded by a point so that they are masked during the normal posting of the contents of the file.

A file of the standard hierarchy is designed to contain the files of configuration: /etc .

The files of configuration can also contain a list of orders to be carried out during the starting of the program. For example, a file " Shell rc" can indicate to the Shell to change current directory, of launching certain programs, creating or to erase certain files, etc

AIX from IBM uses a database of management of objects to store part of its configuration.

In MS-DOS and Windows

Since its origin, MS-DOS is primarily pressed on two files of configuration called Config.sys and Autoexec.bat. They were preserved until Windows 98SE, but were not strictly necessary to the good performance of the applications.

The development of Windows devoted the use of the Register base, jointly with files specialized (like Win .ini or System.ini) to gather the majority of the parameters of configuration.

In Mac OS X

Derived at the same time from NextStep and BSD, Mac OS X a long time preserved files of configuration of the type Unix (files rc and .conf). More and more, Apple directs itself towards files with the format XML, which is also used for the files preferably of the applications (generally with the extension plist ).

See too

Some examples

.htaccess
Prefs.js of Mozilla thunderbird

External bonds

http://www.dotfiles.com/ and http://www.dotfiles.org/: Files of configuration of any kind

Random links: