Система контроля версий исходного кода SCCS: история и особенности

Source Code Control System (SCCS) is a version control system designed to track changes in source code and other text files during the development of a piece of software. This allows the user to retrieve any of the previous versions of the original source code and the changes which are stored. It was originally developed at Bell Labs beginning in late 1972 by Marc Rochkind for an IBM System/370 computer running OS/360. A characteristic feature of SCCS is the sccsid string that is embedded into source code, and automatically updated by SCCS for each revision. This example illustrates its use in the C programming language:
static char sccsid[] = "@(#)ls. c 8.1 (Berkeley) 6/11/93";
This string contains the file name, date, and can also contain a comment. After compilation, the string can be found in binary and object files by looking for the pattern @(#) and can be used to determine which source code files were used during compilation. The what command is available to automate this search for version strings.

In 1972, Marc Rochkind developed SCCS in SNOBOL4 at Bell Labs for an IBM System/370 computer running OS/360 MVT. It was available with the Programmer's Workbench (PWB) edition of the operating system. Release 4 of SCCS was the first version that used a text based history file format, earlier versions did use binary history file formats. Release 4 was no longer written or maintained by Marc Rochkind. Subsequently, SCCS was included in AT&T's commercial System III and System V distributions. It was not licensed with 32V, the ancestor to BSD. The SCCS command set is now part of the Single UNIX Specification. SCCS was the dominant version control system for Unix until later version control systems, notably the RCS and later CVS, gained more widespread adoption. Today, these early version control systems are generally considered obsolete, particularly in the open source community, which has largely embraced distributed version control systems. However, the SCCS file format is still used internally by a few newer version control programs, including BitKeeper and TeamWare. The latter is a frontend to SCCS. Sablime has been developed from a modified version of SCCS but uses a history file format that is incompatible with SCCS. The SCCS file format uses a storage technique called interleaved deltas (or the weave). This storage technique is now considered by many version control system developers as foundational to advanced merging and versioning techniques, such as the "Precise Codeville" ("pcdv") merge. Apart from correcting Year 2000 problems in 1999, no active development has taken place on the various UNIX vendor specific SCCS versions. In 2006, Sun Microsystems (today part of Oracle) released their Solaris version of SCCS as open source under the CDDL license as part of their efforts to open source Solaris.

In SCCS, a delta is a single revision in an SCCS file. Deltas are stored in a delta table, so each SCCS file has its own record of changes. It also provides access to the revision history of files under management. These commands are implemented as argument verbs to the driver program sccs.

$ sccs prt program. c
This command produces a report of source code changes.

Most UNIX versions include a version of SCCS, which, however, is often no longer actively developed.

The late de (who requested the release of SCCS in the early days of the OpenSolaris project) maintained a fork of SCCS that is based on the OpenSolaris source code. It has received major feature enhancements but remains compatible with the original SCCS versions unless using the "new project" mode.

The Heirloom Project includes a version of SCCS derived from the OpenSolaris source code and maintained between December 2006 and April 2007.

GNU offers the SCCS compatible program GNU CSSC ("Compatibly Stupid Source Control"), which is occasionally used to convert SCCS archives to newer systems like CVS or Subversion; it is not a complete SCCS implementation and not recommended for use in new projects, but mostly meant for converting to a modern version control system.

Since the 1990s, many new version control systems have been developed and become popular that are designed for managing projects with a large number of files and that offer advanced functionality such as multi user operation, access control, automatic building, network support, release management and distributed version control. Bitkeeper and TeamWare use the SCCS file format internally and can be considered successors to SCCS. On BSD systems, the SCCSID is replaced by a RCSID starting and ending with ; the corresponding tool is This system is originally used by RCS and added automatically on checkout. The resulting source code revision control identifiers are documented in the NetBSD and FreeBSD style guides for their own code bases. NetBSD defines the custom keyword while FreeBSD defines and a macro renamed
The SRC version control system can also use the SCCS file format internally (or RCS's) and aims to provide a better user interface for SCCS while still managing only single file projects.