In
computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, e ...
, configuration files (commonly known simply as config files) are
file
File or filing may refer to:
Mechanical tools and processes
* File (tool), a tool used to ''remove'' fine amounts of material from a workpiece
**Filing (metalworking), a material removal process in manufacturing
** Nail file, a tool used to gent ...
s used to configure the
parameters
A parameter (), generally, is any characteristic that can help in defining or classifying a particular system (meaning an event, project, object, situation, etc.). That is, a parameter is an element of a system that is useful, or critical, when ...
and
initial settings for some
computer program
A computer program is a sequence or set of instructions in a programming language for a computer to execute. Computer programs are one component of software, which also includes documentation and other intangible components.
A computer program ...
s. They are used for user
applications
Application may refer to:
Mathematics and computing
* Application software, computer software designed to help the user to perform specific tasks
** Application layer, an abstraction layer that specifies protocols and interface methods used in a c ...
,
server processes and
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
settings.
Some applications provide tools to create, modify, and verify the
syntax
In linguistics, syntax () is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure ( constituency) ...
of their configuration files; these sometimes have graphical interfaces. For other programs,
system administrator
A system administrator, or sysadmin, or admin is a person who is responsible for the upkeep, configuration, and reliable operation of computer systems, especially multi-user computers, such as servers. The system administrator seeks to ensu ...
s may be expected to create and modify files by hand using a text editor, which is possible because many are human-editable plain text files. For server processes and operating-system settings, there is often no standard tool, but operating systems may provide their own graphical interfaces such as
YaST
YaST (Yet another Setup Tool) is a Linux operating system setup and configuration tool.
YaST is featured in the openSUSE Linux distribution, as well as in SUSE's derived commercial distributions. It is also part of the defunct United Linux.
YaS ...
or debconf.
Some computer programs only read their configuration files at
startup
A startup or start-up is a company or project undertaken by an entrepreneur to seek, develop, and validate a scalable business model. While entrepreneurship refers to all new businesses, including self-employment and businesses that never intend t ...
. Others periodically check the configuration files for changes. Users can instruct some programs to re-read the configuration files and apply the changes to the current process, or indeed to read arbitrary files as a configuration file. There are no definitive standards or strong conventions.
Configuration files and operating systems
Unix and Unix-like operating systems
Across
Unix-like operating systems many different configuration-file formats exist, with each application or service potentially having a unique format, but there is a strong tradition of them being in human-editable plain text, and a simple
key–value pair format is common. Filename extensions of
.cnf
,
.conf
,
.cfg
,
.cf
or
.ini
are often used.
Almost all formats allow
comments, in which case, individual settings can be disabled by
prepending with the comment character. Often the default configuration files contain extensive internal documentation in the form of comments
[https://opensource.apple.com/source/postfix/postfix-174.2/Postfix.Config/main.cf.default. ][http://opensource.apple.com/source/apache/apache-769/httpd.conf. ] and
man file
A man page (short for manual page) is a form of software documentation usually found on a Unix or Unix-like operating system. Topics covered include computer programs (including library and system calls), formal standards and conventions, and ev ...
s are also typically used to document the format and options available.
System-wide software often uses configuration files stored in
/etc
, while user applications often use a "
dotfile
In computing, a hidden folder (sometimes hidden directory) or hidden file is a folder (computing), folder or computer file, file which filesystem utilities do not display by default when showing a Directory (computing), directory listing. They ar ...
" – a file or directory in the home directory prefixed with a
period
Period may refer to:
Common uses
* Era, a length or span of time
* Full stop (or period), a punctuation mark
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (or rhetorical period), a concept ...
, which
in Unix hides the file or directory from casual listing.
Some configuration files run a set of commands upon startup. A common convention is for such files to have "
rc
" in their name,
typically using the name of the program then an "
(.)rc
" suffix e.g. "
.xinitrc
", "
.vimrc
", "
.bashrc
", "
xsane.rc
". See
run commands
RUNCOM is a CTSS macro command (script) processor.
History
Louis Pouzin created RUNCOM for CTSS circa 1963. He wrote a paper in 1965 describing a design for the Multics shell which includes a brief description of RUNCOM followed by a second p ...
for further details.
By contrast,
IBM's
AIX
Aix or AIX may refer to:
Computing
* AIX, a line of IBM computer operating systems
*An Alternate Index, for a Virtual Storage Access Method Key Sequenced Data Set
*Athens Internet Exchange, a European Internet exchange point
Places Belgium
...
uses an
Object Data Manager
AIX (Advanced Interactive eXecutive, pronounced , "ay-eye-ex") is a series of Proprietary software, proprietary Unix operating systems developed and sold by IBM for several of its computer platforms.
Background
Originally released for the ...
(ODM) database to store much of its system settings.
MS-DOS
MS-DOS
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few ope ...
itself primarily relied on just one configuration file,
CONFIG.SYS
CONFIG.SYS is the primary configuration file for the DOS and OS/2 operating systems. It is a special ASCII text file that contains user-accessible setup or configuration directives evaluated by the operating system's DOS BIOS (typically residing ...
. This was a plain text file with simple key–value pairs (e.g.
DEVICEHIGH=C:\DOS\ANSI.SYS
) until MS-DOS 6, which introduced an INI-file style format. There was also a standard plain text
batch file
Batch may refer to:
Food and drink
* Batch (alcohol), an alcoholic fruit beverage
* Batch loaf, a type of bread popular in Ireland
* A dialect term for a bread roll used in North Warwickshire, Nuneaton and Coventry, as well as on the Wirral ...
named
AUTOEXEC.BAT
AUTOEXEC.BAT is a system file that was originally on DOS-type operating systems. It is a plain-text batch file in the root directory of the boot device. The name of the file is an abbreviation of "automatic execution", which describes its funct ...
that ran a series of commands on
boot
A boot is a type of footwear. Most boots mainly cover the foot and the ankle, while some also cover some part of the lower calf. Some boots extend up the leg, sometimes as far as the knee or even the hip. Most boots have a heel that is cle ...
. Both these files were retained up to
Windows 98SE
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
, which still ran on top of MS-DOS.
An example CONFIG.SYS for MS-DOS 5:
DOS=HIGH,UMB
DEVICE=C:\DOS\HIMEM.SYS
DEVICE=C:\DOS\EMM386.EXE RAM
DEVICEHIGH=C:\DOS\ANSI.SYS
FILES=30
SHELL=C:\DOS\COMMAND.COM C:\DOS /E:512 /P
DOS applications used a wide variety of individual configuration files, most of them binary, proprietary and undocumented - and there were no common conventions or formats.
Microsoft Windows
![Regedit (Wine)](https://upload.wikimedia.org/wikipedia/commons/1/1a/Regedit_%28Wine%29.png)
The early
Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
family of operating systems heavily utilized plain-text
INI files (from "initialization"). These served as the primary mechanism to configure the operating system and application features.
Microsoft: Windows NT Workstation Resource Kit
The API
An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software Interface (computing), interface, offering a service to other pieces of software. A document or standa ...
s to read and write from these still exist in Windows, but after 1993, Microsoft began to steer developers away from using INI files and toward storing settings in the Windows Registry
The Windows Registry is a hierarchical database that stores low-level settings for the Microsoft Windows operating system and for applications that opt to use the registry. The kernel, device drivers, services, Security Accounts Manager, and use ...
, a hierarchical database to store configuration settings, which was introduced that year with Windows NT
Windows NT is a proprietary graphical operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems sc ...
.
macOS
The Property List
In the macOS, iOS, NeXTSTEP, and GNUstep programming frameworks, property list files are files that store serialized objects. Property list files use the filename extension .plist, and thus are often referred to as p-list files.
Property list ...
is the standard configuration file format in macOS
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...
(as well as in iOS
iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also includes ...
, NeXTSTEP
NeXTSTEP is a discontinued object-oriented, multitasking operating system based on the Mach kernel and the UNIX-derived BSD. It was developed by NeXT Computer in the late 1980s and early 1990s and was initially used for its range of proprieta ...
, GNUstep
GNUstep is a free software implementation of the Cocoa (formerly OpenStep) Objective-C frameworks, widget toolkit, and application development tools for Unix-like operating systems and Microsoft Windows. It is part of the GNU Project.
GNUstep ...
and Cocoa
Cocoa may refer to:
Chocolate
* Chocolate
* ''Theobroma cacao'', the cocoa tree
* Cocoa bean, seed of ''Theobroma cacao''
* Chocolate liquor, or cocoa liquor, pure, liquid chocolate extracted from the cocoa bean, including both cocoa butter and ...
applications). It uses the filename extension
A filename extension, file name extension or file extension is a suffix to the name of a computer file (e.g., .txt, .docx, .md). The extension indicates a characteristic of the file contents or its intended use. A filename extension is typically d ...
.plist
.
IBM OS/2
IBM's OS/2
OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...
uses a binary format, also with a .INI suffix, but this differs from the Windows versions. It contains a list
A ''list'' is any set of items in a row. List or lists may also refer to:
People
* List (surname)
Organizations
* List College, an undergraduate division of the Jewish Theological Seminary of America
* SC Germania List, German rugby union ...
of lists of untyped key–value pairs.
The OS/2 INI Files
' by James J. Weinkam.
Two files control system-wide settings: OS2.INI and OS2SYS.INI. Application developers can choose whether to use them or to create a specific file for their applications.
Serialization formats
A number of general-purpose serialization
In computing, serialization (or serialisation) is the process of translating a data structure or object state into a format that can be stored (e.g. files in secondary storage devices, data buffers in primary storage devices) or transmitted (e ...
formats exist that can represent complex data structures in an easily stored format, and these are often used as a basis for configuration files, particularly in open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
and platform-neutral software applications and libraries. The specification
A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard.
There are different types of technical or engineering specificati ...
s describing these formats are routinely made available to the public, thus increasing the availability of parser
Parsing, syntax analysis, or syntactic analysis is the process of analyzing a string of symbols, either in natural language, computer languages or data structures, conforming to the rules of a formal grammar. The term ''parsing'' comes from Lati ...
s and emitters across programming languages.
Examples include: JSON
JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other ser ...
, XML
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. T ...
, and YAML
YAML ( and ) (''see '') is a human-readable data-serialization language. It is commonly used for configuration files and in applications where data is being stored or transmitted. YAML targets many of the same communications applications as Exte ...
.
See also
* .properties
.properties is a file extension for files mainly used in Java-related technologies to store the configurable parameters of an application. They can also be used for storing strings for Internationalization and localization; these are known as P ...
, a file extension mainly used in Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...
* HOCON
HOCON, or Human-Optimized Config Object Notation is a format for human-readable data, and a superset of JSON.
Uses of HOCON
* It is primarily used in conjunction with the Play framework, and is developed by Lightbend.
* It is also supported as ...
, a superset of .properties and JSON
* INI file, a common configuration file format
* JSON
JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other ser ...
, with support for complex data types and data structures
* Run commands
RUNCOM is a CTSS macro command (script) processor.
History
Louis Pouzin created RUNCOM for CTSS circa 1963. He wrote a paper in 1965 describing a design for the Multics shell which includes a brief description of RUNCOM followed by a second p ...
, which explains the historical origin of the "rc" suffix
* TOML
TOML is a file format for configuration files. It is intended to be easy to read and write due to obvious semantics which aim to be "minimal", and is designed to map unambiguously to a dictionary. Its specification is open-source, and receives co ...
, a formally-specified configuration file format
* YAML
YAML ( and ) (''see '') is a human-readable data-serialization language. It is commonly used for configuration files and in applications where data is being stored or transmitted. YAML targets many of the same communications applications as Exte ...
, with support for complex data types and structures
References
{{DEFAULTSORT:Configuration File