The Concurrent Versions System (CVS), also known as the Concurrent Versioning System, is an open-source version control system invented and developed by Dick Grune in the 1980s. CVS keeps track of all work and all changes in a set of files, typically the implementation of a software project, and allows several (potentially widely-separated) developers to collaborate. CVS has become popular in the open source software world and is released under the GNU General Public License. Software development is the translation of a user need or marketing goal into a software product. ... A software release is the distribution, whether public or private, of an initial or new and upgraded version of a computer software product. ... A software release is the distribution, whether public or private, of an initial or new and upgraded version of a computer software product. ... It has been suggested that Maintenance OS be merged into this article or section. ... Linux (IPA pronunciation: ) is a Unix-like computer operating system. ... To meet Wikipedias quality standards, the lead section of this article may need to be expanded. ... FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ... Mac OS X (official IPA pronunciation: ) is a line of proprietary, graphical operating systems developed, marketed, and sold by Apple Inc. ... Computer software can be organized into categories based on common function, type, or field of use. ... Revision control (also known as version control, source control or (source) code management (SCM)) is the management of multiple revisions of the same unit of information. ... A software license is a legal agreement which may take the form of a proprietary or gratuitous license as well as a memorandum of contract between a producer and a user of computer software. ... The GNU logo The GNU General Public License (GNU GPL or simply GPL) is a widely-used free software license, originally written by Richard Stallman for the GNU project. ... A website (alternatively, Web site or web site) is a collection of Web pages, images, videos and other digital assets that is hosted on one or several Web server(s), usually accessible via the Internet, cell phone or a LAN. A Web page is a document, typically written in HTML... // Open Source is a set of principles and practices that promote access to the design and production of goods and knowledge. ... Revision control is an aspect of documentation control wherein changes to documents are identified by incrementing an associated number or letter code, termed the revision level, or simply revision. It has been a standard practice in the maintenance of engineering drawings for as long as the generation of such drawings... Dick Grune is a Dutch computer scientist and university lecturer most well-known for inventing and developing the first version of CVS, the Concurrent Versions System. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... A project is a temporary endeavor undertaken to create a unique product or service[1]. // The word project comes from the Latin word projectum from projicere, to throw something forwards which in turn comes from pro-, which denotes something that precedes the action of the next part of the word... Collaboration is a process defined by the recursive interaction of knowledge[1] and mutual learning between two or more people working together[2] toward a common goal typically creative in nature. ... ... The GNU logo The GNU General Public License (GNU GPL or simply GPL) is a widely-used free software license, originally written by Richard Stallman for the GNU project. ...

Features

CVS uses client-server architecture: a server stores the current version(s) of the project and its history, and clients connect to the server in order to check out a complete copy of the project, work on this copy and then later check in their changes. Typically, client and server connect over a LAN or over the Internet, but client and server may both run on the same machine if CVS has the task of keeping track of the version history of a project with only local developers. The server software normally runs on Unix (although at least CVSNT server supports various flavors of Windows and Unix), while CVS clients may run on any major operating-system platform. Client/Server is a network application architecture which separates the client (usually the graphical user interface) from the server. ... LOCAL AREA NETWORK Local area network scheme A local area network is a computer network covering a small geographic area, like a home, office, or group of buildings. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... The CVSNT Versioning System implements a version control system: it keeps track of all changes in a set of files, typically the implementation of a software project, and allows several (potentially geographically separated) developers to collaborate. ... To meet Wikipedias quality standards, the lead section of this article may need to be expanded. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... It has been suggested that Maintenance OS be merged into this article or section. ...

Several developers may work on the same project concurrently, each one editing files within their own working copy of the project, and sending (or checking in) their modifications to the server. To avoid the possibility of people stepping on each other's toes, the server will only accept changes made to the most recent version of a file. Developers are therefore expected to keep their working copy up-to-date by incorporating other people's changes on a regular basis. This task is mostly handled automatically by the CVS client, requiring manual intervention only when a conflict arises between a checked-in modification and the yet-unchecked local version of a file. Version is a state of an object or concept that varies from its previous state or condition. ...

If the check-in operation succeeds, then the version numbers of all files involved automatically increment, and the CVS server writes a user-supplied description line, the date and the author's name to its log files. CVS can also run external, user-specified log processing scripts following each commit. These scripts are installed by an entry in CVS's loginfo file, which can trigger email notification, or convert the log data into a Web-based format. Data logging is the practice of recording sequential data, often chronologically. ...

Clients can also compare algorithms, request a complete history of changes, or check out a historical snapshot of the project as of a given date or as of a revision number. Many open-source projects allow "anonymous read access", a feature that was pioneered by OpenBSD. This means that clients may check out and compare versions with either a blank or simple published password (e.g., "anoncvs"); only the check-in of changes requires a personal account and password in these scenarios. Open source refers to projects that are open to the public and which draw on other projects that are freely available to the general public. ... OpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution (BSD), a Unix derivative developed at the University of California, Berkeley. ...

Clients can also use the "update" command in order to bring their local copies up-to-date with the newest version on the server. This eliminates the need for repeated downloading of the whole project.

CVS can also maintain different "branches" of a project. For instance, a released version of the software project may form one branch, used for bug fixes, while a version under current development, with major changes and new features, forms a separate branch.

CVS uses delta compression for efficient storage of different versions of the same file. The implementation favors files with many lines (usually text files) - in extreme cases individual copies of each version are stored rather than a delta. In software configuration management (SCM), a delta is a type of file in which the difference (or diff) between two successive versions, is recorded. ...

Terminology

A single project (set of related files) managed by CVS is called a module. A CVS server stores the modules it manages in its repository. Acquiring a copy of a module is called checking out. The checked out files serve as a working copy. One's changes to the working copy will be reflected in the repository by committing them. To update is to acquire the latest changes from the repository in the working copy. It has been suggested that this article or section be merged into Modularity (programming). ... A repository is a central place where data is stored and maintained. ... In the context of computer science and data management, commit refers to the idea of making permanent a set of tentative changes, such as at the end of a transaction. ...

History and status

CVS developed from an earlier versioning system called Revision Control System (RCS), still in use, which manages individual files but not whole projects. Dick Grune has provided some brief historical notes about CVS on his site. To quote: The Revision Control System (RCS) is a software implementation of revision control that automates the storing, retrieval, logging, identification, and merging of revisions. ...

I created CVS to be able to cooperate with my students Erik Baalbergen and Maarten Waage on the ACK (Amsterdam Compiler Kit) C compiler. The three of us had vastly different schedules (one student was a steady 9-5 worker, the other was irregular, and I could work on the project only in the evenings). Their project ran from July 1984 to August 1985. CVS was initially called cmt, for the obvious reason that it allowed us to commit versions independently. The Amsterdam Compiler Kit (ACK) is fast, lightweight and retargetable compiler suite and toolchain written by Andrew Tanenbaum and Ceriel Jacobs, and is Minix native toolchain. ...

– Dick Grune, Dick Grune's website

The code was publicly released to mod.sources on June 23, 1986: the original usenet post is still visible via Google Groups. is the 174th day of the year (175th in leap years) in the Gregorian calendar. ... Year 1986 (MCMLXXXVI) was a common year starting on Wednesday (link displays 1986 Gregorian calendar). ... Google Groups is a free groups and mailing list service from Google. ...

The code that eventually evolved into the current version of CVS started with Brian Berliner in April 1989, with later input from Jeff Polk and many other contributors. Brian Berliner wrote a paper introducing his improvements to the CVS program which describes how the tool was extended and used internally by Prisma, a third-party developer working on the SunOS kernel, and was released for the benefit of the community under the GPL.

Nowadays, a group of volunteers maintains the CVS code. Notably, the development of the Microsoft Windows version of CVS has split off into a separate project named CVSNT and has been more active in extending the feature set of the system, even porting the changes back to the UNIX platform under the name CVSNT. To meet Wikipedias quality standards, the lead section of this article may need to be expanded. ... The CVSNT Versioning System implements a version control system: it keeps track of all changes in a set of files, typically the implementation of a software project, and allows several (potentially geographically separated) developers to collaborate. ...

Relationship with GNU

Historically, the relationship between CVS and the GNU project could appear somewhat ambiguous: the GNU Web site distributed the program, labelling it "GNU package" on one page and "other GPL-licensed project" on another. This was recently clarified when CVS development moved from cvshome.org to savannah.nongnu.org, with CVS officially assigned to the non-gnu category. On the FTP site, the program has traditionally resided in the /non-gnu/ directory and still does. GNU (pronounced ) is a computer operating system composed entirely of free software. ...

Limitations

For each commonly listed limitation of CVS there is also a commonly listed reason:

• Moving or renaming of files and directories are not versioned. It was implemented this way because in the past Refactoring was avoided in development processes. More recently the thinking has changed and refactoring can be managed by an administrator (by moving the RCS file) as it is required. If you develop in Oracle Forms, Cobol, Fortran or even C++ then the CVS reasoning is quite commonly accepted; if you develop with Java then the CVS reasoning may seem counterintuitive.
• No versioning of symbolic links. Symbolic links stored in a version control system can be a security risk - someone can create a symbolic link index.htm to /etc/passwd and then store it in the repository; when the "code" is exported to a Web server the Web site now has a copy of the system security file available for public inspection. A developer may prefer the convenience and accept the responsibility to decide what is safe to version and what is not; a project manager or auditor may prefer to reduce the risk by using build scripts that require certain privileges and conscious intervention to execute.
• Limited support for Unicode text files and non-ASCII filenames. Unix systems run in UTF-8 and so CVS on Unix handles UTF-8 filenames and files natively. If you only work on Unix systems then this response seems reasonable; however when you work on AS/400 and Windows it may not.

Over time, developers have wanted to change the CVS code significantly to add new features, refactor the code and improve developer productivity. This has led to the phrase YACC: "Yet Another CVS Clone". CVS replacement projects include CVSNT (first released 1998), OpenCVS (to be released soon) and Subversion (first released 2004). Refactoring is the process of rewriting a computer program or other material to improve its structure or readability, while explicitly keeping its meaning or behavior. ... In computing, a symbolic link (often shortened to symlink and also known as a soft link) consists of a special type of file that serves as a reference to another file. ... Unicode is an industry standard allowing computers to consistently represent and manipulate text expressed in any of the worlds writing systems. ... UTF-8 (8-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode. ... i5 Model 570 (2006) The Application System/400 (also known as AS/400, iSeries (since 2000) and System i5 (since 2006)) is a type of minicomputer produced by IBM. It was first produced in 1988 and, as of 2006, is still in production. ... The CVSNT Versioning System implements a version control system: it keeps track of all changes in a set of files, typically the implementation of a software project, and allows several (potentially geographically separated) developers to collaborate. ... OpenCVS is a BSD-licensed implementation of the popular Unix version control software called Concurrent Versions System. ... Subversion (SVN) is an open source version control system. ...

See also

Free software Portal

• Revision control, a general overview of version control concepts
• A list and comparison of revision control software
• DCVS, a distributed revision control system based on CVS
• TortoiseCVS, a shell-integrated CVS client for Windows
• Subversion (SVN), an open-source revision control system, which aims to be a replacement for CVS
• CVSNT – open-source revision control system, alternative to CVS
• Bonsai CVS code management system, a tool to report on files, directories, and branches under CVS management.
• Cervisia, a KDE GUI frontend for CVS
• List of file systems

Image File history File links Portal. ... Revision control (also known as version control, source control or (source) code management (SCM)) is the management of multiple revisions of the same unit of information. ... It has been suggested that this article or section be merged with Comparison of revision control software. ... The following tables compare general and technical information for notable revision control and software configuration management (SCM) software. ... It has been suggested that this article or section be merged into Concurrent Versions System. ... TortoiseCVS is a CVS tool for Microsoft Windows released under the GNU General Public License. ... Subversion (SVN) is an open source version control system. ... The CVSNT Versioning System implements a version control system: it keeps track of all changes in a set of files, typically the implementation of a software project, and allows several (potentially geographically separated) developers to collaborate. ... The Bonsai CVS code management system is a computer program designed to help large programming projects productively manage CVS code archives. ... An editor has expressed a concern that the subject of the article does not satisfy the notability guideline or one of the following guidelines for inclusion on Wikipedia: Biographies, Books, Companies, Fiction, Music, Neologisms, Numbers, Web content, or several proposals for new guidelines. ... The following lists identify, characterise and link to more thorough information on computer file systems. ...

References

• David Thomas, Andrew Hunt: Pragmatic Version Control Using CVS (The Pragmatic Programmers, 2003), ISBN 0-9745140-0-4
• Jennifer Vesperman: Essential CVS, Second Edition (O'Reilly, 2006), ISBN 0-596-52703-9
• Per Cederqvist et al: Version Management with CVS, ISBN 0-9541617-1-8, Official reference manual
• Karl Franz Fogel, Moshe Bar: Open Source Development with CVS, ISBN 1-932111-81-6, online

Dave Thomas is a computer programmer and author/editor. ... Andy Hunt (sometimes credited as Andrew Hunt) is a writer of books on software development. ... Moshe Bar is the founder, main developer and project manager of openMosix. ...

External links

The external links in this article or section may require cleanup to comply with Wikipedia's content policies. Please improve this article by removing excessive or inappropriate external links. Please remove this tag when this is done. (talk)

• CVS - Concurrent Versions System (the main web site for CVS - currently unmaintained)
• Dick Grune's page about CVS
• viewvc -- browser interface for CVS repositories
• Documentation at Ximbiot.com
• DevGuy's CVS Information
• SmartCVS, A cross-platform, easy-to-use CVS GUI Client
• Interview with Brian Berliner: CVS creator
• Introduction to CVS
• Getting Started with CVS
• Continuing CVS: Tags, Branches, triggers and CVSWEB.
• Managing Access with CVS.
• CVS Administration introduction
• CVS Best Practices A collection of practices for version control using CVS.
• cvs-nserver
• CVS information on Sourceforge
• OpenCVS - BSD licensed CVS implementation, developed by OpenBSD, still in development
• Commercial Multisite solution for CVS
• Chrooted tunnelled read-write CVS server
• Combined CVS and Subversion tutorial
• Bugzilla/CVS/Wiki integration, a step-by-step guide
• Open Source Development with CVS, a free book about the CVS
• cvslog2web, a log parsing Python script which produces Atom syndication, XHTML output, and permalink pages for each commit